Diffraction grating of high diffraction efficiency and low polarization dependent loss is a key component of the integrated wavelength division-multiplexing device and is of importance in optical communication. But it is difficult for traditional gratings to meet the special requirement of optical communication. A genetic algorithm was used to optimize the profile of grating based on the theoretical calculation method of grating efficiency. A quadratic function was used to describe the grating profile, some original samples were selected, and diffraction efficiency of the sample gratings wascalculated by using the couple-wave approach. Furthermore a few transformations of coefficient of quadratic tuncnons were made by using different operators of genetic algorithm. The diffraction efficiencies of the gratings described by those transformed quadratic function were calculated, the grating profiles that were close to the special requirement were chosen, and others were rejected. Next the transformations of the new sample gratings were made again ,the diffraction efficiency of the gratings described by those transformed quadratic function were calculated again, and then above process was repeated, it was continued until the request was satisfied. By using the method mentioned before, finally we have achieved some optimizational grating profiles that have high diffraction efficiency and low polarization dependence loss. Diffraction efficiency of the gratings achieves more than 90 percent and polarization dependence loss is less than 0.1 dB. It meets the special requirement of optical communication. It is showed that genetic algorithm was used to optimize the profile of grating based on the theoretical calculation method of grating efficiency, it provides theoretical guidance for grating fabrication, and much manpower and material resource were saved.