Our country is one of the largest crude oil producer and has oil and petrochemical industries and is widely used in fields and in the future is predicted to expand considerably in these industries, a result of the water resources of chance of getting infected there is oil in different ways. The aim of this study was to investigate the effect of photocatalytic titanium dioxide nanoparticles to analyze and reduce the toxicity of crude oil water-soluble phase. The fish with an average weight of 89/58 g 7 treatments under the influence of crude oil and titanium dioxide nanoparticles were placed in dark conditions and UV. Tissue injury, including Hypertrophied epithelial cells, Hyperplasia, fusion of secondary lamellae, Aneurysm and … The fish gill tissue was observed. In terms of quantity, the highest and lowest injury in the gill tissue of treated crude oil solution phase prepared in the dark and the control group. The results showed that although all three crude oil solution phase synthesis, solution phase synthesis suspension of nanoparticles of titanium dioxide and titanium dioxide nanoparticles in suspension in oil and water, leading to increased tissue damage in the gills of juvenile common carp, but in equal amounts, affected by the crude oil soluble phase in the dark a lot more in. Based on the results of this study it can be concluded that the process of photocatalytic titanium dioxide particles and ultraviolet light amplification effect is somewhat soluble fraction of crude oil has led to a reduction in adverse effects.