A new experiment for measuring the parameters of polystyrene and polyether-sulphone films using quasi-waveguide method is reported. The films were deposited on the gubstrats with the shape of prism. Leaky mode m-lines of the films were measured. The index and the thickness of the films were determined by using leaky mode equation. The birefringence of the film was obtained with the aid of different polarized laser beam. The measurement errors of the index and thickness are about ±1×10-3, and ±0.01μm respectively.