A Y-branch structure which introduces input waveguide, slow-broadening waveguide and wide-transiting waveguide is designed to reduce the insertion loss of optical power splitter. It’s gradually extended to a 1×8 planar waveguide optical power splitter by using OptiBPM software. Effects of waveguide refractivity, arcus waveguide length, branching angle and input wavelength on output performance of the planar waveguide optical power splitter are investigated respectively, and it is optimized by combining the optimal structure parameters. Simulation results show that the insertion loss and optimal value of output uniformity of the splitter are 9.96 dB, 0.41 dB, respectively. The design parameters and performances of device can meet the requirements of mass production, which has certain reference value for the design and production process of optical splitter.