In this study, at first, the effects of the acute toxicity of agricultural pesticide, diazinon, on adult males of gold fish were determined. After analyzing the results using Probit software, the amount of LC50 was distinguished during 24, 48, 72 and 96 hours. The amount of LC50 was 11.4 in 96 hours and the fish were assorted according to 0.1 and 0.01 percent of LC50 in 96 hours and were put there for about 7 months. Then, the level of total protein, serum glucose, alkaline phosphatase (ALP), alanine transferase (ALT), aspartate amino transferase (AST) was studied. The results showed that fish were affected by high concentration of diazinon, had the lowest ALP (P<0.05) but ALT, AST, glucose and total protein increased significantly (P<0.05).