A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor provides a high efficiency boost DC-DC converting with above 30 times voltage boost rate, which uses a coupling inductor and low voltage switch to absorb circuit induction voltage of a passive regenerative snubber no matter if switch is turned on or off. Such that, a much higher voltage boost rate than the turn rate of transformer and wider range of switching duty cycle is obtained. A bi-directional magnetic energy path is utilized, that is, when switch is turned on the first winding of coupling inductor stores magnetic excited high current energy, and opposite magnetic flux is induced on the second winding at the same time. When switch is turned off the magnetic excited current continues and increases the voltage on the second winding. The second winding has bi-directional magnetic current induced and fully utilizes capacity of transformer's iron core.