Based on the rigorous coupled-wave theory and dielectric slab waveguide theory,a two-dimensional steady physical model is constructed for a silicon-based GaN distributed feedback (DFB) laser. The wave equation is solved by multiphysics field coupling analysis software Comsol Multiphysics,one-dimensional and two-dimensional electric field modes of the DFB laser’s single mode output in visible wavelength region is obtained,and the corresponding relationship between the incident wavelength and the electric field mode is also obtained.Combined with silicon-based optical MEMS technology and micro-machining technology,a wavelength-tunable GaN DFB laser with self-supported gallium nitride periodic photonic grating is proposed.Numerical simulation shows that different single mode wavelength output from the GaN DFB laser can be realized with a certain number of grating lattice,grating height,grating width and active layer thickness.The theoretical analysis and the simulation results are consistent,which proves that this laser model has certain rationality.The simulation data provide a meaningful reference for the realization of the tunable wavelength from the GaN DFB laser.