Power supply unit and wireless network communication system

A power supply unit and a wireless network communication system are provided. The wireless network communication system comprises a wireless network communication device (2) and a power supply unit (3). The power supply unit comprises a power supplier (31), a power detection circuit (32) and a wireless communication module (33). The power supplier converts an AC voltage into a working voltage required by the wireless network communication device. The power detection circuit comprises a rectifier circuit, a voltage divider and regulator circuit and a photoelectric isolation circuit. The rectifier circuit converts the AC voltage into a DC voltage. The voltage divider and regulator circuit provides a reference voltage according to the DC voltage. The photoelectric isolation circuit outputs a power detection signal (AL) according to the reference voltage. The wireless communication module transmits the power detection signal to the wireless network communication device by way of wireless transmission.