The total ionizing dose effects and annealing effects of DVHF2812DF and DVTR2815DF DC-DC power converters were investigated. The typical electrical parameters, such as input current, output current, output voltage, and input current of inhibition mode, as functions of the total dose with different loads and different input voltages were discussed. The relationships between these parameters and the annealing time were observed. The experiment results show that when annealing at room temperature, the trapped holes in deeper energy levels anneal little, which results in dramatic changes of the electric parameters of the DVHF2812DF device when irradiated with extra dose irradiation. However, these parameters go back to the initial values when annealing at high temperature. There are more changes of the electric parameters under the full power loaded situation than other conditions. The input current under inhibition mode can be considered as a sensitive parameter in the evaluation of the radiation-hardened levels of the devices.