In order to overcome the prediction error of classic torque converter model which caused by inaccurate shock loss prediction, a torque converter dynamic model with variable shock loss coefficient was developed. Using bond graph method, the model analyzes working wheel’s performance and energy losses to construct model formulas by geometry parameters, and variable shock loss coefficient method was used to improve model’s accuracy. Test result shows classic constant coefficient method’s percent error can reach to 15%～60% in speed ratio range between 0 and 1, but the result of variable shock loss coefficient is less than 10% in all conditions, which is better than that with classic constant coefficient method.