This paper analyzes the modality of two-dimensional photonic crystal micro-resonators by adopting equivalent refractive index mode. In this paper, it controls the optical field distribution only through altering the thickness of light guide layer, while the parameter like resonator structure and crystal lattice arrangement remain stable. It discusses that it would arrive at a satisfactory photon locality while the refractive index of light guide layer material is gallium nitride , the thickness of light guide layer is and its equivalent refractive index is 2.1.This reveals the influence of micro-resonator light guide layer’s thickness towards the modality, providing a preferable pre-estimate method for the actual research of micro-resonators with higher quality.