The invention discloses a wavelength control device and method of a single frequency laser, which are used for solving the problem that interference curves of the single frequency laser jitter due to centre wavelength frequency drift, so that the change of sensing interference is submerged, thus seriously influencing system performances. Light emitted from the single frequency laser is transmitted to a fiber Bragg grating (FBG), the principle that the FBG can be used to reflect narrow-band light emitted from the single frequency laser, and If the emitted laser has frequency drift, the intensity of the light which is reflected back to the FBG changes is adopted, a high-precision wavelength control module is used for detection to obtain light spectrum change of the centre wavelength of the single frequency laser by received signal intensity of light which is reflected by the FBG, and the high-precision wavelength control module is applied to the single frequency laser in accordance with the light spectrum change, thus the frequency drift of the single frequency laser is reduced, and the centre wavelength of the single frequency laser is recovered to an initial set numerical value.