Abstract: Objective To explore the effect of exposure to vehicle exhaust in pregnant mice on the reproductive function and DNA methylation in male offspring mice. Methods Twenty pregnant mice were randomized into control group and vehicle exhaust exposure group (n=10) and exposed to routine laboratory condition and to vehicle exhaust for 10 consecutive days (8 h per day) in a tunnel with a heavy traffic, where the concentrations of TSP, PM10, PM2.5, SO2 and NOX and the decibel of noise were measured. The offspring mice were raised till reaching maturity, and the epididymides of the male mice were collected to test the weight coefficients, DNA methylation level, and mRNA levels of Aldh7a1 and Rpe. Results The body weight and the weight coefficients of the epididymides and testes differed significantly between the exposure group and the control group (P> 0.05). The concentrations of TSP, PM2.5, PM10 and NOx and the decibel of noise were significantly higher in the traffic environment and the control environment (P<0.05). Reduced representation bisulphite sequencing (RRBS) and Gene ontology (GO) showed that 58 genes had significantly different methylation levels between the two groups, mostly relating to the process of spermatogenesis (P<0.05). Compared with the control group, Aldh7a1 and Rpe mRNA expressions in the testes were down-regulated significantly in the exposure group (P<0.05). Conclusion Exposure of pregnant mice to vehicle exhaust causes damages of the reproductive function in the male offspring mice.