Objective To investigate the concentrations of air benzo(a)pyrene in different areas and the effect of air benzo(a)pyrene exposure on urine neurotransmitter content in 3-5 years old preschool children. Methods The concentrations of air benzo(a)pyrene were detected by the high performance liquid chromatography (HPLC) in different areas (distances from a coking plant 1 000, 2 000, 3 000 and 4 000 m, respectively) and different seasons in a coking plant in the main city of Chongqing. The urine samples were collected from 3-5 years old children who were born in the areas and lived in the areas since birth; and their urine levels of glutamate (Glu), gamma-aminobutyric acid (GABA), dopamine (DA) and serotonin (5-HT) were determined by ELISA assay. Then the relationship between the air benzo(a)pyrene exposure changes and the contents of urine neurotransmitters was analyzed. Results The concentrations of air benzo(a)pyrene decreased with the increase of distance from the coking plant. There were significant differences in the concentrations of air benzo(a)pyrene between different areas in the same season (P<0.05) and among different seasons in the same area (P<0.05). The contents of the children urine neurotransmitters (Glu, GABA, DA and 5-HT) increased with the increase of age in the same area, and decreased with the increase of the concentration of air benzo(a)pyrene in children of the same age. Conclusion Exposure to air benzo(a)pyrene can decrease the urine neurotransmitters in 3-5 years old children, and the detailed reasons and mechanism need further research.