Abstract: The large-scale finite element software MSC.MARC was used to build the coupled thermal-stress FE model of the semi-continuous casting process of 7050 aluminum ingot with the diameter of 550 mm.This model also took account of the latent heat in solidification process and defined the complicated boundary conditions in the semi-continuous casting process.The temperature field and stress field were simulated at different casting speeds and casting temperatures respectively.The results show that in the semi-continuons casting process,compression stresses exist in the outer layer and tensile strees exist in the center of the ingot.Casting speed has great effects on the stress and increase in casting speed and casting temperature result in the increase of cracking tendency.