Abstract: OBJECTIVE To compare the effectivity and safety of ultrasound-guided single erector spinae plane block combined with bupivacaine and with ropivacaine on postoperative analgesia in patients undergoing thoracoscopic surgery. METHODS Sixty patients undergoing thoracoscopic surgery were randomly divided into group of ultrasound-guided single erector spinae plane block with bupivacaine (bupivacaine group, n=30) and group with ropivacain (ropivacain group, n=30). Erector spinae plane block was given to patients before anesthesia induction, and its effect was evaluated by testing the area of block. VAS scores of quiescent and VAS scores of cough were recorded at 1, 6, 12, 24 and 48 h after operation. The frequency and time of use flurbiprofen axetil 48 h after operation were recorded. The adverse events such as pneumothorax after ESP block and the adverse effects such as postoperative nausea and vomiting after operation were observed. RESULTS The block range in bupivacaine group was wider, but there was no significant difference compared with group ropivacain (χ²=1.2, P>0.05). The VAS scores both at quiescent and at cough in group bupivacaine at 1, 6, 12 h after operation were significantly lower than those in ropivacain group (P<0.05). The VAS scores both at quiescent and at cough in bupivacaine group at 24, 48 h after operation were significantly higher than that at 12 h after operation(P<0.05). The average frequency of use flurbiprofen axetil 48 h after operation in bupivacaine group was significantly less than that in ropivacain group(P<0.05). Both in bupivacaine group and ropivacain group, the frequency of use flurbiprofen axetil the second 12 h after operation were significantly higher than that the first 12 h after operation(P<0.05). There were no difference of the incidence of adverse events after ESP block and the adverse effects after operation in two groups(P<0.05). CONCLUSION Both with bupivacaine and with ropivacaine ultrasound-guided single erector spinae plane block on postoperative analgesia patients undergoing thoracoscopic surgery are effective and safe. Both bupivacaine and ropivacaine the duration of postoperative analgesia are only about 12 h. Compared with ropivacaine, bupivacaine is more effective.