A kind of waveguide ring resonator structures based on two-dimensional square lattice photonic crystal is reported. The transmission characteristics are researched by finite element methodnumerical simulation. The results show that by changing the structural parameters of adjustable rods in ring cavity, the resonance frequency of resonance cavity can be effectively adjusted, and according to the diffident resonance modes of the resonance cavity, a good band-pass filter and beam splitting characteristics are achieved. As an example with a 1×2 beaming splitter, by changing the structure parameters of adjustable rods in ring cavity regularly, the intensity modulation to each port output light can be realized. This feature has certain potential application value in the all-optical network.