Ｏｂｊｅｃｔｉｖｅ　To explore the effect of ultrasound-guided single lateral thoracolumbar interfascial plane block (TLIPB) on postoperative patient-controlled intravenous analgesia (PCIA) in patients undergoing posterior midline approach lumbar interbody fusion.　Methods　Forty-two patients, scheduled for posterior midline approach lumbar interbody fusion, were randomly assigned into two groups (n=21), TLIPB combined with PCIA group (group TP) and PCIA only group (group P). Patients in group TP were subjected to TLIPB before operation, then the area of anesthesia was plotted 20 min after TLIPB. VAS scores during resting and coughing were recorded at 1 h (T1), 6 h (T2), 18 h(T3), 24 h (T4) and 48 h (T5) after operation. The pressing times of PCIA pump, the volume of analgesic drugs, and consumption of Parecoxib and the side-effects were recorded as well.　Results　TLIPB in group TP induced sensory loss to pinprick in area covered the ventral rami of the thoracolumbar nerves (L1-L4). The VAS scores at both resting and coughing in group TP were significantly lower than those in group P on T1-T3(P＜0.05). The pressing times of PCIA pump and consumption of Parecoxib were significantly less in group TP than those in group P on 0-1 h postoperatively(P＜0.05). Nausea and emesis were observed in group TP and group P, and did not show any differen(P＞0.05).　Conclusions　Ultrasound?-guided thoracolumbar interfascial plane block for posterior lumbar interbody fusion provides a safe and effective analgesic method for postoperative pain relief.