In an extension cord with wireless timing function, there are included a receptacle housing having more than one flush plug receptacles and internally including a current converter, a power switch and a plurality of electronic relays corresponding to the receptacles; a programmable logic controller in the receptacle housing for controlling the ON/OFF state of the receptacles; a wireless transmission module in the receptacle housing for receiving a wireless signal from a remote device; a power cord connected at an end to the power switch; and an operation and control module located on the receptacle housing and connected to the controller. Thus, timed power supply by each of the receptacles can be set and recorded at the remote device. When the power switch is turned to off, the controller automatically resets the receptacles to ON; and when the power switch is turned to on again, the receptacles will remain to “ON”.