A highly integrated switching power supply and a control circuit are provided. The switching power supply includes a transformer, the transformer comprises a primary winding, a secondary winding and an auxiliary winding, and the control circuit includes: a power switch transistor, configured to control disconnection and conduction of the primary winding of the transformer; a primary current sampling module, configured to sample a current of the primary winding to generate a sampling voltage; and a voltage stabilization control module, configured to turn on or turn off the power switch transistor according to an input voltage, an output voltage of the switching power supply system, and the sampling voltage.