Optical signal splitter was optimized by adjusting the coupling length, coupling width, coupling rod radius between PCSR and waveguide in the two-dimensional photonic crystal structure. As the interactions between PCSRs were considered, electromagnetic wave coupling performances between waveguide and cavity in the structure were analyzed qualitatively by using coupled-mode theory. The transmission characteristics of the two output ports were studied by the FDTD method. It shows that the optical signal splitter based on PCSRs has the characteristics of high normalized transmission ratios, narrow bandwidth, stable signal transmission intensity, broadly tunable ranges of central wavelength in the ranges of design parameters. This structure can separate transmission signal power into two equal parts at the same central wavelength, and it can also separate signals of different central wavelengths. The micro optical signal splitter promises a potential building block of photonic circuits on chip. It is suitable for the designs of wavelength division demultiplexing optical communication systems and photonic integrated circuits etc.