The invention provides a flyback type switching power supply and a control method thereof. The power supply comprises a primary part and a secondary part and has a plurality of working conditions, wherein the plurality of working conditions are respectively corresponding to different load conditions of the flyback type switching power supply and comprise a first type working condition and a second type working condition, the first type working condition adopts a pulse width modulation mode, and the second type working condition adopts a pulse frequency modulation mode. The control method comprises the following steps of acquiring a state conversion parameter according to feedback quality of an output voltage of the flyback switching power supply; and taking a comparison result between the state conversion parameter and different preset values as a judgment criterion for conversion between the first type working condition and the second type working condition, and respectively determining control quantity to be converted under the first type working condition or the second type working condition according to energy conversation during the conversion process between the working conditions and the state conversion parameter. By the flyback type switching power supply and the control method thereof, the plurality of working conditions are smoothly switched, output frequencies are uniform and stable, the audio noise of the system is reduced, the integral efficiency is improved, and the realization complexity of the system is also reduced.