Abstract: With CGSim software,this study performs transient numerical simulation of the process of directionally solidified polysilicon from the beginning of crystal growth to the end of annealing,and investigates the effects of different annealing temperatures and time on the thermal stress and dislocation density in polysilicon ingots. The dislocation and Von-Mises stress are calculated by using an unsteady model of the thermo-elastic stresses（Haasen-Alexander-Sumino model）. The results of this study demonstrated that with the increase in annealing temperatures and time,the thermal stress and dislocation multiplication rate will reduce gradually,after annealing for 1 h,they will decrease greatly,and after annealing for 1 h,the decrease effect will be greatly weakened. The thermal stress and dislocation density under high-temperature annealing are lower than under low-temperature annealing,and annealing at 1250 ℃ for 3 h is a suitable scheme.