This experiment was conducted to investigate the effects of sodium butyrate and weanling days on growth performance and digestive enzyme activity in the intestine of weanling piglets. Ninety-six healthy 21-day-old weanling Duroc×Landrace×Yorkshire piglets with initial weight of (6.00±0.05) kg were randomly divided into 3 groups: control group, trial group 1 and trial group 2. There were 4 replicates of 8 pigs in every replicate. The levels of dietary sodium butyrate supplementation were 0, 1 and 2 g/kg. On day 3, 7 and 14 after weanling, one piglet from one replicate was slaughtered, respectively. The results showed that, on day 3, 7 and 14 after weanling, ADG in trial group 1 increased by 5.0% (P>0.05), 13.4% (P<0.05) and 2.3% (P>0.05), respectively compared with control group. Average daily enzyme activity from day 1 to 14 after weanling: total protease activity of proximal jejunum, distal jejunum and ileum in group 1 and group 2 were higher than those in control group; amylase activity of duodenum in group 1 and group 2 were 28.5% (P>0.05) and 6.4% (P>0.05) higher than those in control group, respectively; compared with control group, amylase activity of proximal jejunum in group 1 and group 2 were increased by 5.9% (P>0.05) and 10.5% (P>0.05), respectively; amylase activity of ileum in group 1 and group 2 were 21.5% (P>0.05) and 22.1% (P>0.05) higher than those in control group, respectively. Sodium butyrate concentration significantly affected lipase activity of duodenum and proximal jejunum (P<0.05). Weanling days significantly affected amylase activity in duodenum and proximal jejunum of piglets and lipase activity in every intestinal tract of piglets (P<0.05), and had significantly effects on total protease activity in distal jejunum (P=0.001). In conclusion, growth performance and digestive enzyme activity in the intestine of piglets were increased by 1 g/kg dietary sodium butyrate supplementation. Lipase activity in intestinal tract of weanling piglets was significantly affected by weanling days (P<0.05).［Chinese Journal of Animal Nutrition, ２００9，２1（５）:719-726］