When incoming light beam enters dielectric reflective mirror with a certain incident angle, there will be a phase shift between the p-polarization and s-polarization. The theoretical model for adhesion layer of interface and surface was established based on the real conditions of interface between layer and atmosphere, and between two neighboring layers. At the same time, this model was used to explain the reason for error of phase shift. Based on optimizing design, when light enters with 54 degree, the phase shift of 270±1° was obtained in the range of 1285~1345nm, meantime, the reflectivity of dielectric mirror maintained over 99.5%. The phase retarder film was prepared with dual ion beam sputter system. The spectrum and the phase of the sample were gained by spectrometer and the Fourier transform infrared spectroscopic ellipsomter, respectively. The results reveal that the samples have phase shift of 262.4±1.8° and the reflectivity reaches over 99.6%. The error mainly originates from non-homogeneous transi