In this present work we report a numerical modeling of methylammonium germanium tri-iodide-based perovskite solar cells using 1D-SCAPS simulation program. To enhance the device performances, improvement of the device structure and both electron transport and hole transport materials is the effective way. Accordingly, this study is mainly focused on exploring of potentially high-stable hole transport materials (HTMs). Diverse HTMs were suggested, including organic and inorganic materials, and investigated to enhance the reproducibility and stability of CH3NH3GeI3-based perovskite solar cells. Among the proposed materials, copper antimony sulfide (CuSbS2) is the most suitable HTM. Hence, employing CuSbS2 as HTM in perovskite solar cell, the power conversion efficiency is significantly enhanced, and its value achieving 23.58%. Therefore, the obtained results make CuSbS2 an excellent candidate for improving the performance of Ge-perovskite solar cells.