In order to solve the problem in complex curve surface forming of ship medium-thick steel plate, the thermal stress forming techniques with high frequency induction heating as heat source were adopted, and the important factors influencing the bending of large-size steel plate were investigated. Then, the influences of heating time, gravity, frequency and power on the large-size steel plate bending were analyzed by COMSOL Multiphysics, and the validity of finite element simulation was verified by experiments. The results show that the heating temperature and stress in the upper surface of steel plate increase significantly after heating for 2 seconds, and the plastic deformation occurs. When the maximum temperature in the upper surface of steel plate reaches 400 ℃, the gravity has a remarkable effect on the bending displacement of large-size steel plate. Compared with the low frequency heating, during the same heating time, the temperature increases rapidly during high frequency heating, and the temperature drops rapidly during cooling. Thus, with the increasing of heating time, the “reversal” phenomenon of the relationship between Y axis displacement and power provides a theoretical basis for determining the optimal heating time of steel plate curve surface forming.