Abstract: Objective To investigate the effects of different types of high-protein nutritional support on nutritional status, immune function and treatment outcome of critically ill patients. 
Methods A total of 90 critically ill patients treated in our hospital were randomly divided into control group, protein powder group and amino acid group, with 30 cases in each group. The three groups were given equal non-protein calories［25 kcal·kg-1·d-1］. On this basis, the control group was only given enteral nutrition emulsion TPF, the protein powder group was given whey protein powder［1.5-2.0 g·kg-1·d-1］, and amino acid group was given compound amino acid［1.5-2.0 g·kg-1·d-1］. The three groups were intervened for 2 weeks. The treatment conditions (duration of ICU stay, duration of mechanical ventilation), incidence of adverse events, nutrition-related indicators and T lymphocyte subsets were recorded before intervention and at 1 and 2 weeks after intervention.  
Results The duration of ICU stay and duration of mechanical ventilation were shorter in protein powder group and amino acid group than in control group; nutritional status and immune function at 1 and 2 weeks after intervention were higher in protein powder group and amino acid group than in control group(P＜0.05). There was no significant difference in the incidence of adverse reactions among three groups(P＞0.05). 
Conclusion High-protein enteral nutrition support can improve the immune function, correct malnutrition,and improve the treatment outcome. 

Key words: critical care nursing,  , nutritional support, diet, high-protein