An integrated optical waveguide grating coupler using gallium nitride and azobenzene polymer composites is designed, and the characteristics of the device are analyzed by simulation. An integrated optical waveguide directional coupler is constructed using two symmetric gallium nitride ridge optical waveguides on a gallium nitride aluminum substrate, and an azobenzene-containing polymethyl methacrylate polymer is coated as a cladding. Based on the photosensitive properties of the azobenzene polymer, a Bragg grating is fabricated by periodic illumination in the region between the two ridge waveguides. The coupling between the modes in the grating coupler is analyzed by the coupled mode theory. Using the coupled mode equations, the output characteristics of each port of the grating coupler are simulated, including the output of each mode as a function of the transmission distance and the amplitude variation under different coupling period conditions. The spectral characteristics of the multi-coupling-period grating coupler are further analyzed, which provides a new scheme for realizing the operation of complex spectrum signal in integrated optical path.