The phase information of the transmitted object, also known as digital holography, can be obtained by the element interference based on prism pair. This method has the advantages of compact structure, stable interference fringe and high measurement accuracy. In this paper, the ray tracing method is used to establish the equivalent model of ray tracing, considering the azimuth rotation of the prism pair and the eccentricity of the inclined plane. The equivalent model is used to simulate the digital holographic interference fringes, and give the analytic expressions of fringe density change and tilt. The interference digital holograms are obtained and the refractive index distribution is inversed for the micro structure optical elements such as single-mode and multimode fibers. The experimental device of micro imaging unit interference is built, and the actual measurement interference pattern is obtained. The experimental results are consistent with the simulation results, which proves the effectiveness of this model.