The branch waveguide and S bend waveguide are presented in this paper. The structure of symmetrical double Y branch S bend waveguide is designed and its bending loss is calculated.The simulation of the change of transmission and bending loss with length for 1/2 Y branch waveguide and 1/4 Y branch waveguide is carried out.The results show that the designed double Y branch waveguide meet the requirement of low loss. Finally, the two dimensional isotropic simulation of the optical field transmission of dual M Z interferometer is carried out, and the optical field transmission graph and refractive index distribution graph are obtained. The results show that the light splitting ratio of the proposed dual M Z interferometer is up to 1∶1∶1∶1.