Objective To he aim of this study was to preliminarily study the toxicity of combined exposure of low-dose of four polycyclic aromatic hydrocarbons. Methods 8-week-old male SD rats were randomly divided into 5 groups with 10 rats each, and 0,10, 50,250 and 1 000 μg/kg·BW dose were continuously administered by gavage. Based on the actual exposure of four polycyclic aromatic hydrocarbons in human body, the proportion of gavage dose was set as benzo [a] pyrene∶benzo [a] anthracene∶chrysene∶benzo [b] fluoranthene=0.99∶2.92∶2.68∶1.68. The rats were sacrificed 30 days after exposure. Biological samples such as serum and organs were taken, organ coefficients were calculated, pathological sections of rat liver were made, pathological changes were observed, and liver function related indexes, oxidative stress related indexes and lipid metabolism related indexes were detected. Results Compared with the control group, the liver structure of the rats in the exposure group was significantly abnormal, the hepatic sinuses were enlarged, and the hepatocytes showed balloon-like change. The liver organ ratio was significantly increased in 1 000 μg/kg·BW group. After 30 d of exposure, serum aspartate aminotransferase (AST) increased significantly in 1 000 μg/kg·BW group (P<0.05). Serum glutathione peroxidase (GSH-Px) in the exposure groups increased significantly at 30 d (P<0.05). After 30 d of exposure, in 1 000 μg/kg·BW group, serum high density lipoprotein cholesterol (HDL-C) decreased significantly and liver cholesterol (TC) increased significantly (P<0.05). Serum triglyceride (TG) of rats in 250 μg/kg·BW increased significantly (P<0.05), and TG in liver of rats exposed to 50 μg/kg·BW or more increased significantly (P<0.05). Conclusion Low dose combined exposure to pah4 has adverse effects of liver injury, oxidative stress and lipid metabolism disorder in SD male rats.