•In this paper, perovskite-type La 0.5 Pb 0.5 MnO 3 nanocrystals with specific surface area was directly prepared by stearic acid method for the first time , where stearic acid was used as reaction solvent, dispersant and complexing agent.•It can not only avoid the disadvantages of the conventional aqueous solution combustion route, which easily leads to the inhomogeneity of the phase as a result of the unavoidable hydrolysis of the metal ions , but also provide the advantage of synthesizing high-purity and homogenous nanocomposites at reasonably simple method.•The precursor and La 0.5 Pb 0.5 MnO 3 were characterized by XRD, FT-IR, SEM, BET, and UV–visible absorption spectra techniques.•The photocatalytic activity for the decolorization of MO under UV light irradiation reveals that the as-prepared La 0.5 Pb 0.5 MnO 3 has excellent catalytic activity.•Above 96% decolorization efficiency of MO in aqueous solution(pH=3) was achieved after 60min of reaction with La 0.5 Pb 0.5 MnO 3 .•This study points out the way to development new, more active perovskite-type catalysts for the wastewater treatment.