The invention discloses a control chip for realizing low-standby power consumption of an AC-DC switch power supply. The control chip includes an output voltage detecting unit, a constant voltage frequency control unit, a standby determination module, a secondary conduction time detecting unit, a constant current frequency control unit, a constant voltage/constant current mode selection unit, a leading edge blanking unit, a peak value current comparison unit, an RS trigger, a driving unit, and a built-in power supply unit. From the aspect of the circuit structure of the switch power supply control chip, the internal circuit structure of the chip can be adjusted under the system standby state, standby signals of the system are generated by the standby determination module and part of unnecessary circuit modules are turned off when the normal standby of the system is maintained, and the work current for chip standby is reduced. Meanwhile, the inner power supply voltage of the chip is reduced under the system standby state, and the standby power consumption of the control chip can be further reduced under the condition that the dynamic performance is not influenced.