Objective To investigate the effect of L3 paravertebral nerve block combined with the compartment block between psoas muscle and sacrum on patient-controlled intravenous analgesia after total knee arthroplasty. Methods 53 patients with ASA1-II grade underwent unilateral total knee arthroplasty for the first time under general anesthesia. They were randomly divided into two groups: Group A and Group B. For patients in Group A, patient-controlled intravenous analgesia was used. For patients in Group B, L3 paravertebral nerve block combined with the compartment block between psoas muscle and sacrum was performed before induction and patient-controlled intravenous analgesia was used for postoperative pain control. General anesthesia was performed in both groups. Block plane was measured within 20 minutes of block in group B, and hemodynamic changes were observed within 20 minutes of block. VAS pain scores were recorded at rest at 30min, 6h, 12h, 24h and 48 hours after operation, and PCIA pressing times at 24 and 48 hours, total infusion volume and total amount of flurbiprofen axetil given after operation were recorded. The incidence of adverse reactions such as nausea, vomiting, itching and respiratory depression was observed. Results There was no significant difference in gender, age, height, weight and operation time between the two groups (P > 0.05).In group B, there was no significant fluctuation in hemodynamics compared with that before nerve block within 20 minutes (P > 0.05).The block plane (ice block method) in the range of L3-S2 was obtained in group B after 20 minutes of blockade. The blockade probability of each dermal segment was different. Compared with group A, , the VAS score at rest in group B decreased significantly at 6, 12 and 24 hours after operation (P < 0.05).There was no significant difference between the two groups at 0.5 h and 48 h after operation (P > 0.05). VAS score at lower limb movement was significantly lower at 12 h after operation than that in group A (P < 0.05), but there was no significant difference between the two groups at 24 h and 48 h (P > 0.05). Compared with group A, VAS score at lower limb movement was significantly lower at 12 h after operation (P < 0.05).In group B, the number of pressing of analgesic pump, the total amount of infusion of analgesic pump and the total amount of flurbiprofen ester were significantly decreased (P < 0.05).here was no significant difference in the number of adverse reactions such as nausea and vomiting between group A and group B (P > 0.05).Conclusion L3 paravertebral nerve block combined with the compartment block between psoas muscle and sacrum can significantly reduce the dosage of opium and other analgesics after total knee arthroplasty, and there is no significant change in vital signs before and after block, and it does not increase the incidence of adverse reactions after operation.