Abstract: Objective To evaluate the toxicity and efficacy of methadone hydrochloride tablets as therapy for patients with severe or refractory cancer pain， and the equivalent dose of morphine tablets （dose conversion ratio）， and its safety. Methods Three hundred and ten advanced cancer patients with severe or refractory cancer pain were consecutively enrolled in this study. The patients used morphine sustained-release tablets for the titration， when their pain intensity NRS≤3 then replace methadone hydrochloride tablets for pain treatment. Results Three hundred and five patients with severe or refractory cancer pain who accept methadone hydrochloride tablets treatment for 2 weeks， pain treatment efficient（response rate，RR） was 88.85％. The RR of bone metastases pain， neuropathy pain and refractory cancer pain were 89.89％， 86.08％， 84.62％ respectively. An average daydose of methadone hydrochloride tablets was 24.56±23.69 mg， 94.43％ of patients within 2 times to take medicine in the 305 patients by the second weekend. One hundred and seventytwo patients with successful dose conversion steady state using morphine sustainedrelease tablets dose was 52.08±40.77mg per day， into the second weekend methadone hydrochloride tablets using dose averaged 18.36 ±10.60mg per day， conversion rate was about 3:1. The incidence of adverse events associated with drugs under 1％ of uroschesis，fatigue， illusion， frequent urination， itching， etc.， under 3％ of the incidence of drowsiness，nausea， vomiting and cold sweat， dizziness rate was 8.06％，constipation rate was 18.06％. There was no case of serious adverse events correlative with Methadone Hydrochloride Tablets， laboratory examination found no effect on liver and kidney function and no electrocardiogram （ECG） change. Conclusion Methadone hydrochloride tablets has definite analgesic effect for chronic cancerous pain， dosage is significantly lower than that of morphine. The transformation rate is slightly higher than the NCCN guidelines recommend. The clinical manifestations of the adverse reactions and the incidence are similar to morphin.