The utility model provides a grating displacement sensor system for detecting the position state of a knife switch of a transformer station, and the system comprises a grating displacement sensor and a background operation and maintenance system. The grating displacement sensor collects an angular displacement change signal of the knife switch of the transformer station, and the angular displacement change signal is transmitted to the background operation and maintenance system. The background operation and maintenance system enables the received angular displacement change signal to be compared with preset switching-on maximum and minimum angles of a system. If the angular displacement change signal is greater than the switching-on minimum angle and less than the switching-on maximum angle, the knife switch is judged to be switched on. The system provided by the utility model can automatically detect the position state of the knife switch of the transformer station, achieves the remote inspection of the knife switch of the transformer station, and saves a large amount of manpower and labor.