Abstract: Total dose experiment of different dose rates of the radiation hardened 100V trench-type N-Channel MOSFET has been studied in this paper. The change trend and mechanism of the device are innovatively put forward with the accumulation of low dose rates and different bias states. The transfer curve and DC parameters are given before and after the device experiment. The two-dimensional numerical simulation is carried out to prove the consistency of the experiment and simulation. The results show that: (1) With the increase of dose at high dose rate, the threshold voltage (V_TH) of the device has a big shift, and the conduction resistance (R_DSON) and breakdown voltage (BV_DS) are basically stable; (2) The total dose effect at low dose rate is significantly different from that at high dose rate. The threshold voltage shift is reduced and the positive drift phenomenon occurs. The increase of the interface charge of the device changes the shift direction of the threshold voltage. There is a certain annealing effect, which leads to the decrease of the difference of the device parameters during the experiment.