A method of fiber Bragg grating sensing demodulation based on self-injection locking is proposed. This method adopts the structure of fiber laser, and the output wavelength of this fiber laser is locked at the reflection wavelength of the sensing grating by self-injection locking. Using the dispersion characteristic of the chirped fiber Bragg grating, the change of the wavelength of the laser is transformed into the change of the length of the resonant cavity. The wavelength change of the laser is measured by the laser beat frequency. The structure and measuring principle of this proposed method are described in detail, and the experimental research is carried out with the example of temperature sensing. This proposed method has the advantages of simple demodulation system, good stability, unlimited sensing distance and good compatibility.