This paper proposes a power terminal design method to obtain a suitable RMS current capacity to fit high-capacity power semiconductor modules. The thermal model considering the power terminal is analyzed and the expression of terminal RMS current capacity is given at first. Then, finite element method(FEM) simulation and corresponding experiments are executed to validate the accuracy of the power terminal thermal model. Finally, the sensitivity of the RMS current capacity to dimensions of the power terminal and thermal conductivity of DBC ceramic is analyzed.