The draw-out power circuit in current transformer is a better way of supplying power for on-line monitoring system in high voltage side of transmission lines.But the circuit has disadvantages of high heat loss and large variation range of rectified voltage values.To deal with these problems，a novel converter draw-out power circuit utilized in two transformer coils is proposed.It can regulate the rectified voltage based on operating characteristics of flux-conservation and pulse width modulation.The circuit is characterized by simple design，high output power of draw-out coil and high efficient.The principle of the circuit is described，relevant parameters are calculated，and the circuit is simulated.At last，a2.5W prototype of forward converter is built and tested.