The present invention discloses a SiC material oxidation state monitoring method and sensor system based on LPFG sensing properties, and belongs to the field of health monitoring of composite structures. The method divides the SiC oxidation state monitoring of a SiC composite material in a service process of into two aspects, namely carbon and oxygen reaction process monitoring in SiC material oxidation and silicone and oxygen reaction process monitoring in SiC material oxidation, respectively monitors the SiC material oxidation process from the two aspects of C and Si, and increases the effective detection accuracy of a SiC composite material oxidative damage monitoring sensor system. The sensing system includes a computer, a spectrometer, a broadband light source, an LPFG silicon carbide material oxidation sensing probe, an optic fiber coupler, a optic fiber connector, an optical switch and an sensing optical fiber. The present invention realizes real-time monitoring of the oxidation state of the SiC matter in SiC composite materials.