The invention discloses a device and a method for performing spectral calibration in an optical frequency domain reflection sensing system through an HCN gas chamber. The HCN gas chamber is additionally arranged in the conventional optical frequency domain reflection sensing device to perform synchronous acquisition, and the scanning start and stop wavelength is determined through the HCN absorption spectral line peak position so as to guarantee the sweep range consistency every time. According to the device and the method, the performance requirement for the present tunable laser can be reduced, the error of spectral shift can be reduced and the distributed measurement accuracy can be effectively enhanced. The invention provides an optical fiber strain measurement method for performing wavelength calibration through the HCN gas chamber based on the OFDR technology. Real-time measurement of the strain or the temperature of each position can be realized by using the OFDR method, the problem of insufficient accuracy of the tunable laser output wavelength can be overcome by using the characteristic of accurate calibration of the HCN gas chamber for the tunable laser sweep signal and real-time accurate measurement of the optical fiber strain can be realized.