The ${I}$ – ${V}$ characteristics of 4H-SiC N/P-channel MOSFETs have been carried out at high temperatures up to 300 °C. Different scattering mechanisms of surface mobility for 4H-SiC N-channel MOSFETs have been studied in this article. Moreover, the temperature dependencies of various scattering mobilities for P-channel MOSFETs are given for the first time. Their temperature dependencies were simulated and analyzed at a temperature ranging from 27 °C to 300 °C. Furthermore, an improved method of extracting trapped charge from transfer characteristic is proposed, such that the density of occupied interface traps in a strong inversion can be extracted. The analysis of experimental results shows that sacrificial oxidation can decrease the occupied interface traps at high temperatures but not much effective at room temperature, and the Coulomb scattering in 4H-SiC P-channel MOSFETs has always been the main mechanism from 27 °C to 300 °C, which is different from 4H-SiC N-channel MOSFETs.