The quantity and composition of the sow's milk production has a significant effect on the growth, health and development of its descendants. This study investigated the effect of adding different levels of folic acid to the diet on the performance of lactating sows. Twenty heads of Changbai × Yorkshire sows were fed a corn-soybean diet (folic acid, 1.3 mg/kg) from pregnancy to litter size (107 days). After littering, the sows were divided into 4 treatments: control group (folate addition level, 0 mg/kg), 1 group (12.5 mg/kg), 2 groups (50 mg/kg), and 3 groups (100 mg/ Kg). The test lasted 21 days. The results showed that the addition of folic acid increased the milk production (P>0.05). Compared with the control group, the addition of folic acid (100 mg/kg) significantly increased the concentrations of milk fat, total and non-lipid substances (P<0.01), and the milk protein concentrations in groups 2 and 3 also showed a significant increase ( P < 0.01). Therefore, the addition of folic acid increased the weaning weight, the average piglet weaning weight and the average piglet daily weight gain (P>0.05). The test results show that during lactation, adding 12.5mg~100mg folic acid/kg can increase milk production, improve milk quality and piglet performance. mMr China Feed Industry Information Network - based on feed, serving animal husbandry