Patients with cancer often experience pain that affects their daily activities and quality of life. The inadequate pain treatments for patients who suffered from the moderate pain are still existed though the analgesic ladder recommended by the World Health Organization contributed outstanding. Current international guidelines recognize that low doses of a step Ⅲ opioid may be used instead of the step Ⅱ for patients with mild⁃moderate pain, although such recommendations are weak. These previous studies showed that to abolish the second step and start directly with a step three opioid will effectively control the pain better with less adverse effects. The effect of clinical analgesia treatment is affected by many factors. In addition to the different efficacy between the step Ⅱ and Ⅲ, the actual conditions such as cancer therapy (antitumor therapy or palliative care), pain types and living distance to the hospital affect the outcome of the patients. Therefore, clinicians need to formulate the analgesic strategy with multi⁃dimensional evaluations in order to improve the curative effect of moderate cancer pain. In our paper, we made efforts to evaluate the efficacy, tolerability and the factors related to adherence to long⁃term opioid therapy of low doses of morphine in comparison with standard doses of weak opioids in the treatment of moderate cancer pain in opioid⁃naive patients in order to provide more references for clinical job.