The invention discloses a starting circuit of a switching power supply. The circuit comprises an input end and an output end VCC. The input end is connected to a positive electrode of the output end after the rectification and filtering of the mains supply, and the output end is connected to a power chip U1. The starting circuit also comprises a voltage dividing circuit connected to the input end,a diode D3, a transistor Q2 and a voltage stabilizing diode Z1. A base of the transistor Q2 is connected to a connection point between the voltage dividing circuit and the input end through a resistor R3, a collector of the transistor Q2 is connected to the connection point and one end of a resistor R3, and an emitter of the transistor Q2 is connected to the output end VCC through the diode D3. Acathode of the voltage stabilizing diode Z1 is connected to a cathode of the diode D3 and the output end VCC through a resistor R5, and an anode of the voltage stabilizing diode Z1 is connected to the ground of the power chip U1 and the ground after the rectification and filtering of the mains supply. According to the starting circuit of the switching power supply, the efficiency of the switchingpower supply at startup is effectively improved by the reasonable connection of various components.