In order to improve the output spectral characteristics of 980 nm semiconductor laser, the expression of transmittivity of dual fiber Bragg grating was deduced by the transfer matrix theory. The influence of fiber Bragg grating length and cavity length on output spectrum was conducted by simulation, the result shows that the fiber Bragg grating length′s influence on output spectrum is greater than fiber Bragg grating cavity length′s, and the width of output spectrum can be reduced by lengthening the fiber Bragg grating length. The dual fiber Bragg grating was fabricated on the tail fiber of 980 nm semiconductor laser to reduce the output spectral width of laser and to improve the stability of the laser output spectrum. The experimental results show that the center wavelength of 980 nm semiconductor laser changes only 0.06 nm when the environment temperature changes within the range of 0℃ to 75℃.