CH3NH3(MA)SnI3, a lead-free halide perovskite, has been recognized as a potential solar cell and thermoelectric material for printed electronics, due to its large absorption coefficient, high charge carrier mobility, long diffusion length of charge carriers and ultralow thermal conductivity. Lü et al. processed MASnI3 by applying a high hydrostatic pressure up to 31 GPa and proved that the structural stability and electrical conductivity of MASnI3 improved after compression. In this study, the bandgap of MASnI3 is studied by combined ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis) and first-principles calculations (DFT)after processed by the high-pressure torsion (HPT) method.