The present invention relates to a tunable laser wavelength detection method and a device. The detection method comprises the following steps of making a drive current-light current curve; making a drive current-central wavelength curve; according to the drive current-light current curve and the drive current-light current curve, obtaining a central wavelength-light current curve; making the central wavelength-light current curve in a first state to obtain the central wavelength of a first optical fiber grating; making the central wavelength-light current curve in a second state to obtain the central wavelength of a second optical fiber grating; comparing the central wavelength of the first optical fiber grating with the central wavelength of the second optical fiber grating, namely the shift amount of the optical fiber grating central wavelength of a to-be-measured physical parameter that is variable; and obtaining the variable quantity of the to-be-measured physical parameter according to the shift amount. The method is simple in principle and easy to realize. By means of the device designed based on the above principle, the variable quantity of the physical parameter can be determined through detecting the shift amount of the excitation central wavelength. Therefore, the device is small in size and low in cost.