Aiming at the problems of complexity, high cost and lack of universal applicability of existing laser wavelength measurement methods, a laser wavelength measurement method based on 3×3 fiber coupler is proposed. The basic principle of the measurement method is deduced theoretically, and the experimental testing system of laser wavelength is built. The fiber delay line(FDL) is used to change delay difference of the interferometer measuring arm, and the half-period number of the interference signal fringe corresponding to the delay change is obtained by using field programmable gate array(FPGA). According to the relationship between half-period number and delay difference, the laser wavelength to be measured is calculated. The experimental results show that the laser wavelength measured by this method is 1310.84 nm and 1550.78 nm respectively, and the laser wavelength measured by spectrograph are 1 310.56 nm and 1 550.63 nm respectively, and the results of the two are almost the same.