This experiment was aimed to study the effects of maternal folic acid supplementation on reproductive performance of gilts and kidney mRNA expression of DNA methyltransferase1 (DNMT-1), p53, Bax, Bcl-2 and insuline-like growth factor-1 (IGF-1) of newborn piglets suffered intrauterine growth restriction (IUGR). Twenty-four gilts were randomly allocated to two groups, control group (C, folic acid 1.3 mg/kg) and folic acid supplementation (F, folic acid 30.0 mg/kg) group with 12 replicates each. Gilts’ reproductive performance within 24 h after parturition and weight of weanling piglets at 21-day-old was recorded. Gilts’ blood samples at the 60th day of pregnancy, and normal body weight (NBW) and IUGR new born piglets’ blood samples and kidney weres collected for serum folic acid concentration test by radio immunoassay. Real-time polymerase chain reaction (RT-PCR) was applied to determine gene expression differences of DNMT-1, p53, Bcl-2, Bax and IGF-1 in kidney. The results showed as follows: supplementation with 30.0 mg/kg folic acid significantly increased serum folic acid concentration of gilts and piglets (P<0.01), but there was no significant difference in reproductive performance of gilts; real-time PCR indicated that relative mRNA expression of DNMT-1 was lower in IUGR+C group than in NBW groups (P<0.05), and transcript expression level of p53 in IUGR+C group was higher than that in NBW groups and IUGR+F group (P<0.01), while Bcl-2 in IUGR+C group was lower than that in NBW groups and IUGR+F group (P<0.01), and there was no significant difference in expression of DNMT-1, p53 and Bcl-2 between IUGR+F and NBW groups (P>0.05); the expression abundance of Bax was higher in IUGR groups than in NBW groups and the opposite pattern was noted for IGF-1 (P<0.05), no significant differences of kidney Bax and IGF-1 expression was noted within IUGR and NBW groups, respectively (P>0.05). Results indicated that supplementation with folic acid had no effect on gilts’ reproductive performance but increased gilts and newborn piglets’ serum folic acid concentration; supplementation with folic acid could prevent the negative effects of IUGR on DNMT-1, p53 and Bcl-2 gene expression.［Chinese Journal of Animal Nutrition, 2010，22（2）:278-284］