Abstract: In order to reduce the bending loss of optical waveguide,the source of bending loss and transition loss of optical waveguide was analyzed. A series of curved line expression were obtained,i.e.,five-power function, six-power function, seven-power function,eight-power function and nine-power function expression. With the help of MATLAB and MAPLE, calculation results show that the curves of the nine-power function is the most smooth, when taking h=125μm, L=800μm(high branching ratio),the loss can be reduced to 4.57dB, which is much smaller than conventional sine function and cosine functions.At last, an optimum route composed of 1×4 optical splitters was designed and simulated in which the energy distribution was symmetric and uniform. This can offer some valuable guidance to the research of Y-type optical waveguide.