Objective To compare the effect of oxycodone,sufentanil and fentanyl on immune function in patients with colon cancer under postoperative analgesia,provide guidance and basis for clinical medication.Methods Ninety patients 49 males and 41 females,aged <65 years,ASA physi-cal status Ⅰ or Ⅱ,were enrolled and randomly divided into 3 groups using a random number table (n=30):oxycodone group (group O),sufentanil group (group SF)and fentanyl group (group F).All patients underwent the same way to maintain anesthesia.The PCIA pump recipe were as follows:group O,oxycodone 2 mg/kg+granisetron 3 mg,added normal saline to 100 ml;group SF,sufen-tanil 0.002 mg/kg+granisetron 3 mg,added normal saline to 100 ml;group F,fentanyl 0.02 mg/kg+granisetron 3 mg,added normal saline to 100 ml;The background volume of PCIA electronic pump was 2 ml/h,the amount of each press was 2 ml,the lock time was 1 5 min,the pump time lasted for 24 h and maintained for 2 days after operation.The percentage of CD4+,CD8+and NK cells in venous blood were recorded at the end of surgery,6 h,12 h,24 h and 48 h after surgery.Results In CD4+,in the time points of 6 h,12 h,24 h after surgery,it was significantly higher in group O than that in groups SF and F (P<0.05);CD8+in group O was higher than that of group F,and CD8+in group F was higher than group SF at the time of 6 h after surgery.The group O was significantly higher than that of the groups SF and F at the times of 12 h,24 h after surgery (P<0.05);In NK cells,at the time points of 12 h,24 h and 48 h after surgery,it was significantly higher in group O than in groups SF and F (P<0.05).Conclusion Three analgesic drugs caused decline in immune function.Sufentanil and fentanyl have the similar effects on immunity,but oxycodone have a relatively small effect on immunity.Oxycodone is a more appropriate analgesic drug for colon cancer under postoperative analgesia.