Objective To evaluate the effect of thoracic paravertebral nerve block (TPVB) on postoperative chronic pain in patients undergoing thoracic surgery.Methods One hundred and forty patients of both sexes,aged 25-64 yr,with body mass index of 18-24 kg/m2,of American Society of Anesthesiologists physical status Ⅰ or Ⅱ,scheduled for elective thoracoscopic radical resection of lung cancer,were divided into 2 groups (n=70 each) using a random number table method:control group (group C) and TPVB group (group P).Two-point (T4,6) TPVB was performed on the affected side under ultrasound guidance before anesthesia induction,and 0.5％ ropivacaine 20 ml was injected into each puncture site in group P.Sufentanil 0.1 μg/kg was intravenously injected at 10 min before the end of operation in group C.Analgesic pump was connected at the end of operation in two groups,and patient-controlled intravenous analgesia was performed with sufentanil.The patients were followed up after operation.Sufentanil 0.1 μg/kgwas intravenously injected when visual analogue scale score ≥4.The total consumption of sufentanil and the number of requirements for rescue analgesia were recorded at 48 h after operation in both groups.The patients were followed up to 2 months by telephone after operation,the occurrence of postoperative chronic pain was recorded,and the effect of pain on daily life and grade of treatment measures were evaluated.Results Compared with group C,the total consumption of sufentanil and the number of requirements for rescue analgesia were significantly reduced,and the impact of postoperative chronic pain on daily life and grade of treatment measures for pain were decreased in group P (P＜0.05).There was no significant difference in the incidence of postoperative chronic pain between the two groups (P＞ 0.05).Conclusion Although TPVB cannot reduce the incidence of postoperative chronic pain,it can relieve the degree of postoperative chronic pain in patients undergoing thoracic surgery.