In order to realize the wavelength division multiplexing function of light wave and improve the radiation efficiency of light wave, a two-dimensional photonic crystal wavelength division multiplexer based on double ring resonator cavity structure is designed. Firstly, the structural parameters of photonic crystal are designed. Through the coupling of resonator cavity and microcavity, the light waves with different frequencies are selected, and the photonic crystal filter model is designed. Then, according to the mode coupling theory, the optimal coupling conditions between the backbone waveguide and the resonator cavity are determined, and the wavelength division multiplexer is designed. Finally, the scattering dielectric column is added and the relative position between the two resonators is adjusted to optimize the wavelength division multiplexer to improve the transmittance of light wave. The experimental results show that the multiplexer structure realizes the improvement of 1.562 μm、1.544 μm、1.451 μm、1.436 μm、1.366 μm and 1.322 μm, the maximum radiation efficiency of light wave can reach 96% and the device size is only 13.44 μm× 16 μm。