Disclosed is a low-power consumption standby circuit device comprising a primary power supply, a secondary power supply, a first control switch and a control circuit module. An input terminal of the primary power supply is connected with an external power supply via the first control switch. An output terminal is connected with external loads to power the external loads. An input terminal of the secondary power supply is connected to the external power supply and an output terminal is electrically connected with the control circuit module. The control circuit module comprises an MCU module and a signal receiving circuit, wherein the MCU module controls the on-off of the first control switch. An air conditioner adopting the circuit device achieves a quasi zero-watt standby target through a reasonable power supply distribution and enhancing the anti-interference capability of a main chip. A control method for the air conditioner is also disclosed.