In the present study the effects of  lethal and sub- lethal levels of malation in male gold fish, Crasius auratus, have been studied. In this regard, first of all, fish were exposed with lethal concentration levels of malation (15-23 mg/l) and 96 h median lethal concentration, LC₅₀, calculated as 12.5 mg/l for this fish. Then fish were exposed to sub-lethal  levels including 0.1 LC50 ( 2.35 mg/l ) and 0.01 LC₅₀ (0.235 mg/l) of  malation for 7 months. Then effects of this toxicant on hematocrit, hemoglobin, the number of  red blood cell and white blood cell, MCH, MCHC, MCV, alanin amino taransferas, alkalin phosphatase, asparat amino transferas, total protein, testestron and glucose of blood were evaluated. hematocrit, hemoglobin, the number of  red blood cell and white blood cell, MCH, MCHC and MCV were significant (p<0.05) between experiment treatments as fish which were exposed to the concentration of  0.1 LC₅₀  of malathion toxicant had lower hematocrit, hemoglobin, the number of  red blood cell and white blood cell, MCH and MCHC compare to control group. The lowest levels of alanin amino taransferas, total protein, testestron and glucose were observed in 0.1 mg/liter and minimum levels of alkalin phosphatase and asparat amino transferas found in control group.  Histopathological study were characterized by hepatocyte degeneration, defuse hepatocyte vacuolization, accumulation of melanomacrophage and focal necrosis in the liver of fish that exposed with concentration of 0.1 LC₅₀. On the other hand this fish that exposed with concentration of  0.01 LC₅₀  showed moderate pathologic signs in the liver.