Objective To observe the efficacy and safety of the modified patient- controlled subcutaneous analgesia by epidural catheter with three-hole for patients undergoing radical mastectomy Methods Ninety patients aged 35 y-68 y undergoing Radical Mastectomy were randomly divided into three groups ( n=30, each): group TCPCSA (patient-controlled subcutaneous analgesia with placement trocar ) , group ECPCSA (patient-controlled subcutaneous analgesia with placement epidural catheter with three-hole)and group PCIA (patient-controlled intravenous analgesia) . All cases received sufentanil 100 μg + lidocaine 200 mg + dexamethasone 10 mg) using patient-controlled analgesia pumps which were set up with bolus dose of 0.5 ml, lockout interval of 15 min, and backgound infusion rate of 2 ml/h. The scores of VAS and RSS, MAP, HR, RR and SpO2 were recorded at 4, 8, 16, 24 h and 48 h after surgery respectively. Times of bolus and side effects (nausea, vomiting, respiratory depression, etc ) were also recorded. All patients received the same induction and maintenance of anesthesia Results MAP, HR, RR, SpO2, VAS and RSS, incidence of nausea and vomiting did not differ significantly amonggroups ( P>0.05). The incidence of detachment of catheter or trocar was lower in the group ECPCSA (0%) than that in the group TCPCSA（16.7%）and the group PCIA(6.7% )(P<0.05). The overall satisfaction is higher in the group ECPCSA (100% )than the group TCPCSA(80%)and the group PCIA (73.3%) (P<0.05). Concusions The modified patient-controlled subcutaneous analgesia with epidural catheter could provide good analgesia with less side effects, improve patients’ satisfaction, and have advantages of less incidence in detachment of catheter.