A method for measuring the film parameters of waveguide by using grating couplers is studied. The parameters for waveguide thin film of zinc sulfide prepared on a substrate of F1 glass by the vacuum evaporation and epoxy resin prepared on a substrate of K.9 glass by a dip-coating were measured. The grating periods used were 1200 mm-1, 1800 mm-1 and 2400mm"1 respectively. The measurement results indicate: the observed values of effective index of thin film waveguide modes are in good agreement with the calculated ones. The accuracies of the calculated values from measured values of waveguide mode effective index Nm and thin film refractive index % are better than measured values of thin film thickness are 2.8~0.1%. We believe that the grating coupler can be used as an effective equipment for rapid and accurate determination of waveguide thin film parameters in the field of guided wave optics and semiconductor technology. Ib is just as effective as the prism coupler and has its own features. The prism couplers with grating structure are also discussed briefly.