Abstract: Objective : To investigate the effect of 6% hydroxyethylstarch replacing xenogenous blood tranfusion on perioperative immune system in patients with cancer. Methods : Sixty patients who underwent malignant tumor resection were randomly divided into two groups. In group B 30 patients were treated with blood transfusion and in group B 30 patients received hydroxyethylstarch infusion during surgery. The blood samples were collected before anesthesia and on the 3rd,7th day after operation. Enzyme-linKed immunosorbent assay (ELISA) is used to dected the level of sIL-2R and IL-2, the cytoactive of NK cell were measured by the method of LDH release. Results : sIL-2R increased in two group, but the amount of sIL-2R was markedly increased in group B, on the 3rd and 7th day after operation (P<0.05); Il- 2 and the cytoactive of NK cell were markedly decreased after operation in group B(P<0.05), while there was not significant difference in group B. Conclusion : Perioperative xenogenous blood transfusion can depress immune system in patients with cancer, hydroxyethylstarch did not affect immune system.