As one of the important ways to realize the "meter" benchmark, the accuracy of laser wavelength is of great significance in the fields of metrological calibration, precision measurement and spectral detection. However, at present, the wavelength reference based on the absorption spectrum of reference materials can only be used for the metrological calibration of single wavelength, and the calibration methods for the wavelength of broadband light source are limited. This paper mainly researches on broadband continuous tuning laser wavelength calibration technology. Using the characteristics of wide spectrum, optical frequency traceable to atomic frequency standard and high stability of femtosecond laser frequency comb, the continuous optical wavelength of broadband tunable light source during tuning output is measured. Finally, the measurement of instantaneous value of the tunable laser in the tuning output process under the bandwidth of 1 nm is realized. Meanwhile, the frequency modulation nonlinearity of tunable laser in 121 GHz bandwidth is evaluated by using the measurement results.