OBJECTIVE： To compare the effects of equilibrium amino acid and it rich in branched chain amino acid on nutrition metabolism after surgery and prognosis of severe abdominal trauma patients. METHODS： A total of 60 severe abdominal trauma patients selected from our hospital during Sept. 2016-Jun. 2017 were divided into group A and B according to block randomization， with 30 cases in each group. Both groups were all given iso nitrogenous and iso caloric parenteral nutrition support on the basis of surgery and routine treatment after surgery； group A was additionally given 8.5％ Compound amino acid injection （18AA-Ⅱ） 1.2 g/（kg·d） for 12 h each day at least； group B was additionally given 10％ Compound amino acid injection （20AA） 1.2 g/（kg·d） for 12 h each day at least. Both groups were treated for 7 d. The levels of nitrogen balance and serum protein （total protein， albumin， prealbumin and transferrin）， plasma amino spectrum were observed in 2 groups before and after treatment. Hospitalization time， survival rate， the occurrence of complication and ADR were compared between 2 groups. RESULTS： Two patients of group A and one patient of group B were discharged， and totally of 57 patients completed the study. Before treatment， there was no statistical significance in the levels of nitrogen balance， serum protein or plasma amino spectrum （P＞0.05）. After treatment， the cumulative nitrogen balance of group B was significantly better than that of group A. The level of nitrogen balance was increased significantly in observation group 3-7 d after treatment and control group 5-7 d after treatment. Since 4 d after treatment， the level of nitrogen balance in group B was significantly better than control group， with statistical significance （P＜0.05）. The levels of albumin， prealbumin and transferring in group A were decreased significantly， and were significantly lower than group B， with statistical significance （P＜0.05）. The levels of glycine and threonine in 2 groups were increased significantly. The level of arginine in group B was decreased significantly， while the levels of valine and branched chain aimino acid were increased significantly； those indexes of group B were significantly lower or higher than those of group A respectively， with statistical significance （P＜0.05）. The incidence of gastrointestinal complications and disruption of wound， total incidence of complications in group B were significantly lower than group A， with statistical significance （P＜0.05）. There was no statistical significance in hospitalization time， survival rate or the incidence of infection between 2 groups （P＞0.05）. No obvious ADR was found in 2 groups. CONCLUSIONS： Compared to equilibrium amino acid， equilibrium amino acid rich in branched chain amino acid can further improve and maintain the nitrogen balance， the levels of serum protein and plasma amino acid of severe abdominal trauma patients after surgery with low incidence of complication.