The experiment was conducted to study the effects of dietary potassium butyrate supplementation on reproductive performance, blood biochemical indices and milk composition of lactating sows. Fifty-six PIC sows, with similar parity, body condition and expected date of delivery, were allocated into four groups with fourteen replicates, each replicate containing one sow. Sows were fed with basal diet supplemented with 0 (control), 0.075%, 0.150% and 0.300% potassium butyrate, respectively. The experiment was carried out from day 90 of pregnancy to day 21 of lactation. The results showed as follows: from day 8 to day 14, and day 1 to day 21 of lactation, average daily feed intake in the 0.150% group was increased by 18.50% and 18.07%, respectively, compared with the control group (P＜0.05) and increased by 11.73% and 12.21%, respectively, compared with the 0.075% group (P＜0.05), but there was no significant difference between 0.150% and 0.300% groups (P＞0.05). Average daily gain of piglets in the 0.150% group (210.23 g/d) was significantly higher than that in the control group (177.66 g/d) (P＜0.01 ). On day 1 of lactation, milk fat and milk protein contents in the 0.150% group were significantly higher than those in the control group (P＜0.05). On day 14 of lactation, milk fat and milk total solid contents in the 0.150% group were significantly higher than those in other groups (P＜0.05), and milk lactose and milk protein contents in the 0.150% group were significantly higher than those in the control group (P＜0.05). On day 1 of lactation, plasma glucose and triglyceride contents in the 0.150% group were significantly higher than those in control and 0.075% groups (P＜0.05), but there was no significant difference between 0.150% and 0.300% groups (P＞0.05). On day 1, 14 and 21 of lactation, no significant differences were observed among the four groups on plasma free fatty acid content (P＞0.05). These results demonstrate that dietary potassium butyrate supplementation can enhance the feed intake of lactating sows and the average daily gain of piglets, and improve the milk composition of sows. ［Chinese Journal of Animal Nutrition, 2010，22（5）:1367-1373］