The invention discloses a power frequency communication synchronous detection method and device for an industrial power grid, belonging to the technical field of power system network structure and communication. The power frequency communication synchronous detection device for the industrial power grid is formed by connecting a master station device and a telecommunication terminal of a distribution transformer end to a high voltage transmission line of a substation; down driving equipment in the master station device firstly sends synchronous information based on M sequence coding before sending down data information; when the communication terminal receives a signal, a composite signal is formed according to modulation coding, and the synchronous detection is realized on the composite signal through short-window Morlet complex wavelet transformation; after the synchronous detection is successful, the communication terminal can carry out data demodulation; because the synchronous information can be enhanced and does not need a detection threshold, the invention adapts to the severe channel environment of the industrial power grid and can utilize a house transformer of the substation as a signal modulation transformer, thereby greatly facilitating the application of power frequency communication in the industrial power grid.