For the polymeric electro-optic waveguide, approxi mate expressions of propagation constant and loss coefficient are derived by usi ng perturbation theory according to coupled mode theory of the ideal optic waveg uide, thereby complicated complex calculations for finding the solution of eigen value can be simplified to simple real calculations. Numerical calculations show that these approximate solutions are in good agreement with exact solutions. Th e approximate formulae and characteristics curves can be provided as reference of design and preparation of polymeric electro-optics waveguide and its device.