In order to investigate the effects of neutral and acid protease on growth performance of weaned piglets, a feeding trial was conducted and 135 healthy Duroc×Landrace×Yorkshire crossbred weaned piglets with an average weight of (7.2±0.9) kg in a 3×3 crossing design trial were randomly assigned to 9 groups (3 replicates per group and 5 piglets per replicate). Supplemental levels of neutral protease were 0, 0.004% and 0.008%, respectively, and supplemental levels of acid protease were 0, 0.004% and 0.008%, respectively. The experiment lasted for 28 d, including early period (1～14 d) and later period (15～28 d). The results showed that neutral and acid protease had significant effects on average daily gain (ADG) and feed/gain (F/G) during early period, later period and the whole period, but no significant effects on diarrhea ratio (P＞0.05). Supplementation with 0.008% neutral protease and 0.004% acid protease simultaneously had significant increasing effects on ADG and average daily feed intake (ADFI) and decreasing effects on F/G (P＜0.05), but F/G was the highest when only 0.008% acid protease was added in feed. In conclusion, neutral and acid protease could improve the growth performance of weaned piglets to some degree, and supplementation with 0.008% neutral protease and 0.004% acid protease simultaneously was the best. And their interaction on growth performance was found.［Chinese Journal of Animal Nutrition, 2009，21(6):993-997］