The invention relates to a wireless network automatic networking method based on power-on synchronization and belongs to the technical field of wireless networking. According to the method, a master control device and slave devices are powered on at the same time and are to be networked, the master control device performs automatic networking with the method of judging whether the slave devices are in the same network according to the power-on time, if the power-on time of the slave devices is matched with that of the master control device, the slave devices are networked to the master control device, and network information of the master control device is transmitted to the slave devices so that networking can be completed; otherwise, the slave devices are not networked to the master control device. Automatic networking of a wireless network in a family can be fast achieved, and missing networking and error networking are avoided. Besides, the master control device and the slave devices are respectively provided with a networking time window after being powered on, networking is allowed in the time windows, otherwise networking is rejected, and therefore other networks are prevented from being added into the network or interference caused by networking between adjacent networks can be prevented.