Formamidinium tin iodide (FASnI(3)), as one promising Pb-free halide perovskite, has received extensive attention. But perovskite solar cells (PSCs) based on FASnI(3) films have yet to realize the high power conversion efficiency (PCE) achieved in its Pb-based counterparts. To investigate the limitation of FASnI(3)-based perovskite solar cells with inverted p-i-n planar structures, the influences of various parameters on the device performance are analyzed through device simulation. The results reveal that defect density at front hole transport material (HTM)/absorber interface is critical for high efficiency. And it is interesting to note that the doping density, rather than the doping type and its space distribution, dominates the device properties, and an upper limit of 1 x 10(16) cm(-3) is achieved. In addition, the response of device to band offset is investigated, and an optimum electron affinity of 3.9 eV is obtained. Finally, the effects of relative permittivity and thickness of the absorber with different carrier lifetime are studied. A maximum PCE of 9.75% is achieved at absorber thickness of 300 nm with carrier lifetime of 0.1 ns? These results show that optimizing the interface property and band offset, improving the stability of Sn2+ and reducing the defect density of absorber layer are the main challenges for high-performance FASnI(3)-based PSCs in the future research.