Abstract: A field-circuit coupling model for merged PiN schottky（MPS） silicon carbide（SiC） diode was proposed in this paper. Both the electrical characteristics of diode chip in the surge current condition and the influence of chips temperature coupling were considered in this model. Firstly, a physical model was established by lumped charge modeling method based on the MPS chip structure, and a thermal model consistent with the a SiC module package structure and size was established by finite element simulation software. Secondly, the field-circuit coupling model based on the electrical model and thermal model of MPS SiC diode was established by PSpice-Comsol co-simulation platform. The time scale difference between circuit simulation and thermal simulation was solved by multi-rate simulation strategy. The model can be used to do the characterization and simulation analysis of electrical and temperature distribution characteristics for the MPS SiC diode. Finally, the established model was simulated and verified by experiment results of a Cree 1200 V/300 A SiC module under surge current. The results show that the proposed field-circuit coupling model has the advantages of high simulation accuracy and efficiency. It provides an analytical method for the study of the working characteristics of SiC diodes with MPS structure under extreme conditions.