Abstract: The origin of the Changbaishan volcanic province （CBSVP） has been considered to mainly relate to the Pacific Plate subduction. Therefore, it is necessary to dynamically reconstruct the Pacific Plate subduction processes towards and beneath the CBSVP since the Cenozoic in order to investigate its origin. This reconstruction requires consideration of the seismic discontinuities in the upper mantle. There are two main global seismic discontinuities in the upper mantle: the 410-km and 660-km discontinuities, which have been considered as phase transition boundaries. The 410-km discontinuity represents the exothermic boundary of the α-olivine to β-spinel transition, featuring a positive Clapeyron slope. Consequently, negative buoyancy is generated and attaches to a subducting slab near this discontinuity, accelerating the slab’s subduction into the the mantle transition zone （MTZ） and slightly enhancing the transportation of upper mantle materials and the penetration of the slab through the 660-km discontinuity. However, some investigators hold opposing views regarding the effects of the olivine-spinel transition on the penetration of the 660-km discontinuity. The Clapeyron slope （γ₄₁₀） and thickness （δh₄₁₀） of the 410-km discontinuity range from 1.0 to 3.8 MPa/K and from 2 to 40 km. The 660-km discontinuity is the endothermic boundary of the transition from ringwoodite to bridgmanite and magnesiowüstite. This boundary, generally speaking, exhibits a negative Clapeyron slope. Consequently, positive buoyancy is generated and attaches to a subducting slab near the discontinuity, hindering the slab’s sinking into the lower mantle. Some investigators have considered this to be the primary cause of stagnant slabs in the MTZ, while others do not believe that the buoyancy resulting from the phase transition at this boundary is sufficient to compensate for the density of a cold subducting slab. The Clapeyron slope （γ₆₆₀） and thickness （δh₆₆₀） of the 660-km discontinuity range from −0.4 to −6 MPa/K and from approximately 2 km to 70 km. The δh₆₆₀ is between 35 km and 70 km in Northeast China. These results indicate that the two discontinuities have the wide ranges of the Clapeyron slopes and thicknesses. It favors predicting a stagnant slab in the MTZ mapped by seismic tomography, using a geodynamic model that incorporates a γ₆₆₀ ranging from −1.5 to −8 MPa/K, without considering the 410-km discontinuity, while when considering the 410-km discontinuity, the γ₄₁₀ generally takes 3 to 4 MPa/K and the γ₆₆₀ −2 to −6 MPa/K. It may well reproduce the stagnant Pacific slab in the MTZ beneath East Asia using geodynamic models that consider either γ₆₆₀＝−1.5 — −3 MPa/K and δh₆₆₀＝40 km or γ₆₆₀＝−2 MPa/K and δh₆₆₀＝40 km in the absence of the 410-km discontinuity. Alternatively, when considering the 410-km discontinuity, it may use models with either γ₄₁₀＝4 MPa/K, γ₆₆₀＝−2 MPa/K and δh₄₁₀＝δh₆₆₀＝64 km or γ₄₁₀＝3 MPa/K and γ₆₆₀＝−3 MPa/K in the presence of the 410-km discontinuity. These studies have provided us with basic knowledge of the effects of the two discontinuities on slab subduction dynamics, but in the meantime, we find that previous researches have presented a wider range of Clapeyron slopes and thicknesses for the 410-km and 660-km discontinuities, aiming to replicate the stagnant slab structure in the MTZ. Consequently, it is essential to clarify the impacts of these two discontinuities on the dynamic process of Pacific Plate subduction, as well as the slab structure, westward movement distance, and sinking depth within the mantle. Therefore, in this study, we set up a series of data-assimilation three-dimensional geodynamic models that incorporate varying values of γ₄₁₀, γ₆₆₀, δh₄₁₀ and δh₆₆₀ to predict the westernmost positions, bottom depths and subduction processes of the Pacific Plate since the Cenozoic. It is found that: ① The γ₄₁₀, to a certain degree, affects the westward movement distance of the Pacific slab in the mantle, while it slightly influences the sinking depth of the slab. As the γ₄₁₀ decreases, the average movement distance increases gradually, and the sinking depth becomes slightly shallower. The maximum differences are about 80 km and 50 km for the distance and sinking depth, respectively, over a range of γ₄₁₀ from 0 to 6 MPa/K; ② With the increase of |γ₆₆₀|, the effect of γ₄₁₀ gradually weakens. When |γ₆₆₀|≥4 MPa/K, the effect of γ₄₁₀ can be almost ignored; ③ The γ₆₆₀ has significant effects on both the westward movement distance and sinking depth of the Pacific slab in the mantle. When |γ₆₆₀|≤5 MPa/K, the average slab westward movement distance increases as |γ₆₆₀| increases. However, when |γ₆₆₀|＞5 MPa/K, the situation reverses, that is, the larger the |γ₆₆₀|, the smaller the average slab westward movement distance. The sinking depth consistently becomes shallower with the increase of |γ₆₆₀|. The maximum differences exceed 300 km and 600 km for the distance and sinking depth, respectively, over a range of γ₆₆₀ from −1 MPa/K to −6 MPa/K; ④ Both δh₄₁₀ and δh₆₆₀ have slight effects on the dynamic processes of the Pacific slab and the slab structure within the mantle; ⑤ A geodynamic model that merely considers the effects of both 410-km and 660-km discontinuities may predict the westernmost position of the Pacific slab in the modern mantle reasonably, but it struggles to reproduce the slab’s sinking depth reasonably.