In this study, anatase Li+-TiO2 composite nano-photocatalyst was prepared by sol–gel method. The ability of Li+-TiO2 composite photocatalyst to photocatalyze the degradation of aquatic product wastewater and the factors affecting the degradation were studied. Li+-TiO2 composite photocatalysis has a high photocatalytic degradation efficiency for aquatic product processing wastewater. There are six factors that affect the photocatalytic degradation ability: the amount of lithium doping, the amount of composite photocatalyst, pH value, the initial concentration of ammonia nitrogen, the initial concentration of COD and the amount of H2O2 solution. In the experiment of photocatalytic degradation of wastewater treated by various factors, when the doping amount of lithium is 3%, the dosage of Li+-TiO2 is 1.2 g/L, pH value is 7, the initial concentration of ammonia nitrogen is 80 mg/L, the volume fraction of H2O2 is 5%, the initial concentration of COD is 300 mg/L, and the light is exposed for 2 h. The photocatalytic degradation of ammonia nitrogen and COD in aquatic wastewater was 72.4 and 69.4%, 79.2 and 67.4%, 80.0 and 64.1%, 80.7 and 66.3%, 74.5 and 69.3%, 70.3 and 81.3%, respectively.