The invention discloses an externally pasted fiber grating sensor for a diaphragm filter plate, and a detection system and method. The sensor comprises a plurality of fiber grating packaging pasters that are pasted to a diaphragm filter plate of a filter press and are arranged in a matrix mode. The fiber grating packaging pasters having the same structures consist of substrates, fiber gratings arranged on the substrates, and conduction fibers connected with the fiber gratings; the fiber gratings and the substrates are packaged in an integrated mode to detect the diaphragm filter plate strain and/or a temperature change. According to the invention, the fiber grating sensor uses the substrate made of a glass-fiber-reinforced epoxy resin composite material, so that the slight strain at the frame of the diaphragm filter plate can be monitored precisely. Besides, a sensor-based intelligent health monitoring system of the diaphragm filter plate is also provided; and real-time, reliable, and overall health state monitoring based on the slight strain at the side frame of the diaphragm filter plate can be realized.