Abstract: During the operation of GaN-based converters, the rise in junction temperature caused by device self-heating significantly affects their dynamic on-resistance. To accurately evaluate this characteristic, this paper adopts a multi-group double-pulse test method and constructs a high-temperature test bench with stable and controllable junction temperature to comprehensively test and evaluate the dynamic on-resistance of two commercial GaN devices with different structures. The study details and compares the degradation behaviors and variation patterns of the dynamic on-resistance in these two GaN devices under different drain-source voltages and junction temperatures. The results indicate that the dynamic on-resistance is significantly influenced by the junction temperature and exhibits non-linear differences depending on the switching mode, junction temperature, and bias voltage.