In order to verify the influence of beam intensity distribution on film thickness, the distribution of epitaxial film was simulated by theoretical calculation of beam current distribution, and the data were compared with the samples of epitaxial experiment. The results confirmed our guess, which can partially explain the uneven distribution of film thickness. Using the formula to calculate the distribution of beam intensity, the thinnest point should be 73.26% of the thickest point. While the thickest point of the experimentally tested film thickness was 8.1582 μm, the thinnest point was 5.9362 μm, the ratio was 72.76%, which was basically consistent with the calculation results. Therefore, it can be determined that the beam intensity distribution has a certain influence on the film thickness. However, the film thickness of the actual material is not only affected by the beam distribution, but also related to other process parameters. Due to the comparison between theoretical calculations and experiments, the results obtained are more accurate and reliable than those obtained by simple experiments.