Abstract: The laboratory results of stick-slip of a fault with weak barrier were presented in this paper. The weak barriers were simulated by two isolated saw kerfs which meet at right angles with the sawcut representing the fault. The results show that the weak barriers obviously can stop (or called stop-fracture) or delay the unstable stick-slip extending process. The a stop-fracture effects depend on the depth of the saw kerf and average normal stress n which exert on the saw cut representing the main fault. The effects of stop and delay increase with l,and increase with x but not monotonously. The average delay time tdn curve is like a V shape. The spatial distribution of apparent fracture energy,G,ploted against distance along the main fault shows that there is no high G in the front of the stop points in the unstable extending process,which indicates that the weak barrier is another stopbreak mechanism. It may stop or delay the unstable extending process of stick-slip by absorption of strain energy. The results show some complex time and space features of stick-slip events under conditions represented in this sample,which can help us undersdand the relation between strong earthquake sequences. Further research on the stop or delay effects of the extending process can help us perfect the stick-slip mechanism in seismology.