To operate a converter at cryogenic temperatures, understanding the characteristics of power semiconductor devices is critical. This paper investigates the temperature and current dependence of the dynamic performance of five types of SiC power MOSFETs at 77 K. The turn-on and turn-off lasting time and the corresponding switching energy loss are extracted from a series of double-pulse tests. The transient peak voltage of cryogenic MOSFETs is lower, but the switching time is higher than the room-temperature ones. Moreover, power-exponential functional relations with the operating currents are found in the experiments. These results obtained lay some technical bases for exploring superconducting power electronics.