Abstract: The energy-gaining power supply of current transformer has the heating problem when the bus current is high, which affects the service life of power supply. For this reason, this paper proposes a design method of the energy-gaining power supply for the current transformer based on self-adaptive power output control. Based on the analysis of the power acquiring principle of current transformer, the load equivalent model of energy-gaining coil of the current transformer is established, and the relationship between the output power of the coil and the bus current is derived. By controlling the on-off state of the bidirectional thyristor, the purpose of controlling the power output of energy-gaining coil is achieved, and it is ensured that the power supply does not heat up at a large current. An implementation form of self-adaptive power output control circuit is given. By establishing its equivalent model, the relationship between the conduction angle and the bus current is derived. Finally, the experiment shows that the power prototype made according to the proposed design method can work in a low heat consumption state in a wide current range, which verifies the feasibility of the proposed method.