The thermal characterization and hotspot localization of SiC MOSFETs are essential for obtaining a better understanding of their failure mechanisms. In this study，we developed a lock-in infrared(IR)microscopy system to analyze the thermal behavior of the device. We applied a pixel-by-pixel emissivity correction method to obtain accurate thermal emissivity and temperature distribution maps. We employed lock-in IR thermography to identify the leakage paths and precisely locate the thermal hotspots. We systematically evaluated the influence of the lock-in parameters，including the integration time，modulation frequency，and heating power，on the localization performance. The results indicate that the thermal emissivity of the SiO₂ passivation layer is approximately 0. 9， whereas that of the aluminum source metal is approximately 0. 2. Under a heating power of 0. 89 W，the peak surface temperature reached approximately 41 °C. When compared with the conventional pixel-wise correction，lock-in IR thermography enables rapid and effective hotspot localization at low power levels，with improved accuracy achieved through extended integration time，higher frequency，and increased power.