Abstract: LaFeO₃, La_0.8Sr_0.2FeO_3-δ and nonstoichiometric (La_0.8Sr_0.2)_x FeO_3-δ (x=0.97, 1.03) nanoparticles were fabricated via a simple solvothermal method. The morphologies and structures of the samples were characterized by XRD, TEM, UV-Vis, XPS and so on. Malachite green (MG) photodegradation was used as a model reaction to investigate the photocatalytic activity of these samples under the maximum absorption wavelength (616.9 nm). The results indicate that the doping of Sr²⁺ reduce the grain size and cause lattice defects and oxygen vacancies V_O^.. to be formed, which are in favor of hindering the recombination of electrons and holes, increasing the quantum efficiency. Doping Sr²⁺ and changing nonstoichiometry make the catalysts have strong absorption in visible region and large specific surface area. The specific surface area of (La_0.8Sr_0.2)_1.03FeO_3-δ is the largest (20.164 4 m²/g) and the visible degradation efficiency of (La_0.8Sr_0.2)_1.03FeO_3-δ is the highest(83.8%) among the catalysts. The photocatalytic activities of doped Sr²⁺ and nonstoichiometric LaFeO₃ are higher than those of pure LaFeO₃.