Objectives To evaluate the effects of enteral nutrition(EN)and parenteral nutrition(PN)support in critically ill surgical patients. Methods 80 patients who could not eat were randomized into two groups:one group receivedEN,the other group received PN. The nutrition parameters including nitrogen balance, serum levels of albumin, prealbumin, transferrin and retinal-binding protein,immunity function parameters including immunoglobulin A, immunoglobulin G,immunoglobulin M,and natural kill cell activity, and patients'tolerability parameters including glutamic-oxalacetic transaminase, glutarmic-pyruvic transaminase, blood urea nitrogen and creatinine,and plasma glucose were compared. Results After 10 days'therapy,the two groups all turned from negative nitrogen balance to positive nitrogen balance. The nutrition parameters and immunity function parameters increased significantly in both groups and the latter in group EN increased more. For tolerability parameters, blood sugar in group PN increased obviously and no change in EN group. ConclusionsBoth EN and PN play a rde in nutrition support and elevation of immunity function. Patients tolerate well. EN has better effects on elevation of immunity function and patients tolerate better compared with PN.