Local anesthesia is routinely recommended for percutaneous transforaminal endoscopic discectomy (PTED). However, the intense intraoperative pain remains a serious problem. The purpose of the current study is to find a safe and effective method to alleviate the intense pain during PTED for lumbar disc herniation (LDH) under local anesthesia.This study retrospectively analyzed 63 LDH patients who accepted PTED under local anesthesia. Thirty-one patients received intramuscular injection of morphine before PTED, while the other 32 were not. The 10 points visual analogue scale (VAS) was used to assess the patients' maximum leg and back pain. Patients were asked to grade their experiences of surgery and anesthesia on a 5-point Likert-type scale after the surgery. Modified Mac Nab Criteria were used to evaluate the surgical outcomes after 3-month follow-up.The intraoperative VAS scores of patients who accepted preoperative intervention decreased significantly. The postoperative VAS scores of both groups showed no significance. Patients who received preoperative intervention reported a higher subjective satisfaction rate with the surgery experience. According to the Modified Mac Nab criteria, the surgical outcomes of both groups were similar through the 3-month follow-up. After injection of morphine, 4 patients complained nausea and 2 patients experienced vomiting.Preoperative intramuscular injection of morphine could reduce the patients' pain during the PTED surgery and improve the patients' satisfaction without affecting the surgical outcome. Except for a higher incidence of nausea and vomiting, this method is relatively safe and convenient.