Objective To evaluate the safety and clinical efficacy of high intensity focused ultrasound (HIFU) for patients with solid tumors under sedation and analgesia. Methods Sedation and analgesia were induced with i.v. fentanyl(1?g/kg) and midazolam (0.03mg/kg) in 81 patients with benign or malignant solid tumors. High intensity focused ultrasound (HIFU) ablation treatment was then performed. The short-term effect and adverse events of sedatives and analgesics, as well as the effect of HIFU ablation treatment were observed. Results One hundred and twelve HIFU courses were performed on 81 patients, among them 23 patients with benign solid tumors received 26 courses of treatment, and 58 patients with malignant solid tumors, received 86 courses of treatment. A total of 153 foci were targeted. It was estimated that in 81% of all the patients, the tumor size was decreased by 50%, including 72.2%(52/72)of malignant tumors and 97.4%(37/38)of benign tumors. Tumor markers of malignant tumors decreased by more than 50% in 81.3%(13/16) of patients, and remission rate of tumor-related symptoms reached 77.9% (30/39). The adverse events during sedation and analgesia were nausea, reduction in the respiratory rate, visual hallucination, and that of HIFU were pain and swelling. No comblications with severity surpassing grade Ⅲ were found as a result of either sedatives, analgesics or HIFU treatment. Conclusion Sedation and analgesia are relatively safe, effective and feasible during HIFU treatment for solid tumor.