LiInO₂ nanoparticles (NPs) have been successfully synthesized by a sol-gel method. The structure of the as-synthesized LiInO₂ NPs were characterized using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) analysis technologies. The photocatalytic performances of samples were evaluated using the methyl blue (MB) as a model dye pollutant. Additionally, the photocatalytic degradation mechanism for MB of the LiInO₂ NPs were also proposed. The results demonstrated that the as-prepared LiInO₂ presented a LiFeO₂ structure with the uniform size about 50~100 nm. The calcination temperature can severely impact the structure and photocatalytic performance of the LiInO₂ NPs. The degradation rate of MB was 92% under simulated sunlight using 300W xenon lamp for 90 min. The trapping experiments of the reactive species showed that the holes played an important role in the process of the MB degradation. The results obtained from this work suggested that the LiInO₂ NPs would have potential applications in wastewater treatment.