The paper aims to solve the problems of thermal damage and difficulty in real-time temperature monitoring in surface grinding of composite materials by cup wheel and study the dynamic variation law of grinding temperature field. In this paper, by analyzing the material removal mechanism in surface grinding by cup wheel, a non-uniform heat source model under cylindrical coordinate system with different function distribution in circumference and radial direction was proposed. And based on this model, an numerical model of grinding temperature field was established to predict grinding temperature. Finally, a calculation method of temperature prediction error caused by heat carried away by debris was proposed. The validation experiments of thermocouple temperature measurement were carried out, and the predicted and experimental values under different heat source models were compared to verify the accuracy of the non-uniform heat source and its temperature field model. Compared with the temperature field under the uniform heat source, which under the non-uniform heat source was more agreement with the actual temperature field, and the error of temperature prediction was reduced from about 23% to within 6.5%. The experimental results show that grinding depth has a great influence on grinding temperature. To ensure the accuracy of temperature prediction, it is necessary to consider the error caused by heat carried away by debris during high efficiency deep grinding.