Background Systematic pain management of children is not enough in China, and there is no summary of pain in children with sarcoma. Methods Collect clinical data of newly diagnosed sarcoma patients admitted to the Medical Oncology Department of Beijing Children’s Hospital from October 2018 to December 2020. Pain assessment was completed by part-time palliative doctors. Children with pain received analgesic treatment and regular assessment. Results A total of 188 newly diagnosed sarcoma patients were included. 37 patients (19.7%) suffered from pain. 6 cases (16.2%) had mild pain, 17 (46.0%) moderate, and 14 (37.8%) severe. The daily life of 31 patients (83.8%) was affected by pain. 26 cases (70.3%) had bone invasion. The analgesic rate was 54.1% (20/37) before admission and 89.2% (33/37) after admission. 9 cases were treated with oral morphine regularly, all of whose pain relieved before chemotherapy, and the actual dose of morphine was 0.14±0.034mg/kgQ4H when the target was reached. No serious adverse reactions were observed. The total time of morphine application after chemotherapy was 5-9 days (median 6 days), and there was no withdrawal reaction during the process of reduction. Conclusion The pain in children with newly diagnosed sarcoma was mainly moderate to severe pain, and the incidence of pain in sarcoma originating from bone or invading bone was higher and the intensity was more severe. Patients who received standardized pain assessment and regular analgesic reached pain relief quickly, and no serious adverse reactions were observed within the recommended dosage.