Ultrathin freestanding thin-film filters with high transmittance in the extreme ultraviolet band can be prepared using metallic as well as nonmetallic materials. However, improper process parameters and experimental conditions can directly cause film rupture during preparation. This study performed a finite element simulation of the key preparation steps of freestanding thin films and calculated the equivalent stress on the film under different conditions. The results indicate that the thin film sample, when placed perpendicularly to the liquid surface, experiences the minimum equivalent stress. During liquid transfer, higher fluid flow velocity leads to greater equivalent stress on the thin film. Further, the equivalent stress on the thin film is mostly distributed near the inner-diameter edge of the external support frame. The improved preparation process based on these simulation results is more stable than the original process, reducing the negative impacts of adverse process conditions and parameters on the thin-film transfer process, as well as the uncertainty caused by human factors. In addition, the repeatability of the film preparation process is improved, and the yield of the ultrathin freestanding extreme ultraviolet thin-film filters is enhanced.