In this study, using density functional theory, we calculated the band structure and photoelectric properties in a series of 12.5% B-doped (B = Ge, Sn, Ca, and Sr) CsPbI3 perovskite systems. It is found that Ge doping can improve the structural stability and is more conducive to applications under high-pressure or by applying stress via calculating the bond length, formation energy, elastic properties, and electronic local function. In addition, the optimal direction for applying stress is achieved according to the elastic properties. Furthermore, in terms of electronic properties, the reason of energy band variation and the influence of chemical bond on the structural stability of doped α-CsPbI3 are investigated. The possibility of the applications of the CsPb0.875B0.125I3 perovskite is explored based on the optical properties. Thus, the theoretical study of the CsPb0.875B0.125I3 perovskite provides novel insights into the design of next-generation photoelectric and photovoltaic materials.