Objective To investigate the effect of ultrasound⁃guided anterior quadratus lumborum block at the lateral supra⁃arcuate ligament（QLB⁃LSAL）or posterior quadratus lumborum block（QLB2）on postoperative analgesia and postoperative recovery quality in patients undergoing laparoscopic radical resection of rectal cancer. Methods A total of 80 patients who had received laparoscopic radical resection of rectal cancer were selected. The patients were randomly divided into two groups：QLB⁃LSAL group（group A）and QLB2 group（group Q），40 in each group. Sufentanil consumption 48 h after surgery，time to the first PCA，24h QoR⁃40 score after surgery， VAS scores on resting and exercise status at 2 h，6 h，12 h，24 h and 48 h after surgery，incidence of relief anal⁃ gesia at 48 h after surgery，satisfaction with analgesia，early postoperative recovery，and occurrence of adverse reactions were compared between the two groups. Results As compared with group Q，the consumption of sufentanil 48 h after surgery，the scores on resting and exercise VAS at 6 h，12 h，and 24 h after surgery in group A were significantly decreased（P < 0.05）. Time to the first PCA in group A was significantly longer than that in group Q （P < 0.05）. The 24 h QoR⁃40 score was significantly higher in group A than in group Q（P < 0.001）. There were no significant differences between the two groups in the incidence of relief analgesia 48 hours after surgery，satis⁃ faction with analgesia 48 hours after surgery，first flatus，first ambulation，postoperative nausea and vomiting and other adverse reactions（P > 0.05）. Conclusions In laparoscopic radical resection of rectal cancer，QLB⁃LSAL， compared with QLB2，can provide better analgesic effect，reduce use of postoperative opioids，and improve the postoperative recovery quality in patients.