Deformation of casing during solidification process puzzles many engineers and scientists for years.In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool.The traditional methods compute the thermal stress of both the casting and the mold.It suffers the problem of massive calculation and failure of convergence.This paper proposed an improved Mold Surface Element Method, which is able to simulate the complicated interaction between casting and mold in efficiency and provide satisfied precision for engineering.Two practical casting products are used to verify the proposed method.The simulation results agree well with the results observed in practical products.The proposed method is believed to benefit the production practice and provide theoretical guidance.