In this paper,a method for the determination of the complex tensor components (real and imaginay parts) of electro optic contants of dye doped polymer films is used by a Mach Zehnder interferometer.With this method,the complex electro optic tensors of disperse red 1 (DR1) dye molecules doped in polymethylmethacrylate (PMMA) films were measured.The influence of multiple reflections in polymer film on the experimental results is discussed and corrected.