A wind power generation system and a control method thereof are provided herein. The wind power generation system includes a doubly-fed generator, a generator-side converter, a grid-side converter and an auxiliary converter. The doubly fed generator includes a stator winding and a rotor winding. The stator winding is coupled to a grid. The generator-side converter is coupled to the rotor winding. The grid-side converter is coupled between the generator-side converter and the grid. The auxiliary converter includes a first side and a second side. The first side is coupled to the stator winding. The second side is coupled between the generator-side converter and the grid-side converter. The generator-side converter, the grid-side converter and the auxiliary converter use the same DC bus.