INTRODUCTION: The effectiveness of remimazolam in suppressing oxidative stress, inflammatory reactions, and its lung-protective effects in patients undergoing thoracic surgery with one-lung ventilation (OLV) remains unestablished. This study aimed to investigate the protective effects of remimazolam against oxidative stress and inflammatory damage in such patients. METHODS: This randomized controlled trial evaluated 88 patients with lung tumors who underwent single-lung ventilation for thoracoscopic lobectomy under general anesthesia. Patients were randomly divided into an experimental group (R group) and a control group (Con group), with 44 patients in each group. The R group received an intravenous injection of 0.2 mg/kg of remimazolam during anesthesia induction. During anesthesia maintenance, a continuous intravenous infusion of remimazolam at a rate of 0.2 mg/kg/h was administered. The Con group received routine anesthesia. Preoperative and postoperative levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6 were detected. Changes in blood pressure and heart rate were recorded at four time points: upon entering the operating room (T1), immediately after tracheal intubation (T2), immediately after incision (T3), and immediately after surgery completion (T4). The postoperative awakening time, post-anesthesia care unit (PACU) stay time, and frequency of adverse reactions were also recorded. RESULTS: Postoperatively, the R group exhibited significantly higher levels of SOD and GSH-Px, and significantly lower levels of TNF-α and IL-6 compared to the Con group ( DISCUSSION: Low-dose remimazolam (0.2 mg/kg) can provide protective effects against oxidative stress and inflammatory injuries in patients undergoing OLV, without affecting awakening time or PACU time.