Abstract: Different gate-source field-plates of GaN HEMTs with p-GaN gate structure were compared and investigated using Synopsys? TCAD tool.The simulation results showed that a new electrical field was introduced at the end of source field-plate and the breakdown voltage of the double gate-source plates structure was improved to 1365 V.A new peak of electric filed was produced in the interval gate field-palte by interval gate and source field-plates structure,and the breakdown voltage was further improved to 1478V.The suppression of the electrical field in gate plate gap by souce field-plate was decreased in the gatesource both interval structure and the highest breakdown voltage 1546V was achieved.