The invention discloses a high-gain boost converter realized based on a coupling inductor boost unit and a control method thereof. The high-gain boost converter includes a coupling inductor, a power switch tube, a clamping circuit, a boost circuit and an output filter circuit. The primary coil of the coupling inductor is connected with an input power supply Vin. The front end of the clamping circuit is connected with the primary coil of the coupling inductor, and the back end is connected with the boost unit. The secondary coil of the coupling inductor is connected into the boost circuit. Thefilter circuit is connected to the back end of the boost circuit. The gate of the power switch tube is connected with a converter control signal voltage Vgs, the source is connected with the negativeelectrode of the input power supply Vin, and the drain is connected between the primary coil of the coupling inductor and the clamping circuit. Large increase in gain can be achieved with small duty cycle.