Abstract: Combining deterministic method with probabilistic analysis and taking BZ28-2 offshore petroleum platform as a research object，we have made a detailed investigation on seismo-geological background, causative faults and their seismic activity, temporal and spatial distribution of seismicity, expectant magnitude and expectant distance of destructive earthquakes and actual occurrence probability.Based on these investigations the scenario earthquake parameters and response spectrum of near field strong ground motions under different scenario earthquakes are comprehensively determined. Application of this method provides better results on design ground motion and site response spectrum parameters. At the same time, this method offers an important reference for seismic fortification of projects in sea regions.