The effect of high overdrive voltage on the positive bias temperature instability (PBTI) trapping behavior is inves-tigated for GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) with LPCVD-SiNx gate dielectric. A higher overdrive voltage is more effective to accelerate the electrons trapping process, resulting in a unique trapping behavior, i.e., a larger threshold voltage shift with a weaker time dependence and a weaker temperature depen-dence. Combining the degradation of electrical parameters with the frequency-conductance measurements, the unique trapping behavior is ascribed to the defect energy profile inside the gate dielectric changing with stress time, new inter-face/border traps with a broad distribution above the channel Fermi level are introduced by high overdrive voltage.