Abstract: Objective To evaluate the changes in the nutritional status and immune function in patients with colorectal cancer after operation. Methods The indexes of the nutritional status and immune function were measured in 40 patients with colorectal cancer before and after operation and compared with the control group. Results The levels of IgM, IgG, prealbumin and transferrin were lowered after operation in these colorectal cancer patients (P<0.05), but no significant difference was noted after operation in the control group. Conclusion The nutritional status and immune function in colorectal cancer patients obviously deteriorate after operation.