The unfavorable morphology and inefficient utilization of phase transition reversibility have limited the high-temperature-processed inorganic perovskite films in both efficiency and stability. Here, a simple soft template-controlled growth (STCG) method is reported by introducing (adamantan-1-yl)methanammonium to control the nucleation and growth rate of CsPbI3 crystals, which gives rise to pinhole-free CsPbI3 film with a grain size on a micrometer scale. The STCG-based CsPbI3 perovskite solar cell exhibits a power conversion efficiency of 16.04% with significantly reduced defect densities and charge recombination. More importantly, an all-inorganic solar cell with the architecture fluorine-doped tin oxide (FTO)/NiOx/STCG-CsPbI3/ZnO/indium-doped tin oxide (ITO) is successfully fabricated to demonstrate its real advantage in thermal stability. By suppressing the inductive effect of defects during the phase transition and utilizing the unique reversibility of the phase transition for the high-temperature-processed CsPbI3 film, the all-inorganic solar cell retains 90% of its initial efficiency after 3000 h of continuous light soaking and heating.