To understand the developmental toxicity and the maternal toxicity of formaldehyde (FA), pregnant mice were injected celiac with FA, from the 6th day to the 19th day after the pregnancy. After the birth of fetal mice, the single cell gel electrophoresis (SCGE) was applied to test the DNA damage in liver cells of the maternal mice and of the fetal mice. The experimental results obtained from fetal mice indicate that FA does not induce DNA damage at the low concentration (0.2 mg/kg, P > 0.05), while it could induce DNA breakage at higher concentration as 1.0 mg/kg (P < 0.01). Moreover, DPC(DNA-protein crosslinks) was also initiated at the concentration as 2.0 mg/kg (P > 0.05). When the concentration was up to 20.0 mg/kg, almost all of the DNA is completely joined to form DPC (P > 0.05). The experimental results of pregnant mice indicate that DNA breakage could initiate at relatively low concentration (0.2 mg/kg). Meanwhile, the damage effect was obviously enhanced with the increasing of concentrations (1.0 mg/kg, P < 0.01; 2.0 mg/kg, P < 0.01; 20.0 mg/kg, P < 0.01). No significant increase in DPC formation was observed in pregnant mice, indicating that of all the concentrations of FA tested in the experiment, the DNA damage mainly attributes to DNA breakage. These results suggested that FA has both the maternal toxicity and the developmental toxicity.