Objective:To retrospectively analyze the bone marrow smears of neuroblastoma and rhabdomyosarcoma in children and summarize the morphological characteristics of the two types of tumors invading the bone marrow to provide reference for the identification and differential diagnosis.Method:A total of 908 bone marrow specimens were collected from the outpatient and inpatient children who were diagnosed as Neuroblastoma and Rhabdomyosarcoma by pathological tissue or lymph node biopsy in Sun Yat-sen University Cancer Center from January 2013 to July 2020. Of which, 231 cases of tumor bone marrow metastasis were detected. Bone marrow smears were observed and analyzed, classified and summarized according to the morphological characteristics of tumor cells.Result:A total of 231 cases of bone marrow metastases were detected, including two types of tumors, 217 cases Neuroblastoma, with an invasion rate of 34.23%; 14 cases Rhabdomyosarcoma, with an invasion rate of 5.11%. The tumor cells of neuroblastoma were arranged in a pseudo-chrysanthemum or wall-like arrangement and most of them were surrounded by nerve fibers. According to cell size, they could be divided into large cell type and small cell type. Rhabdomyosarcoma cells were mainly medium in size, with vacuoles in the nucleus, and double, triple and multinucleated cells can be seen. The cytoplasm was gauze-like, with bead-like vacuoles at the edges. According to the morphological characteristics of neuroblastoma and rhabdomyosarcoma, they can be differentiated from acute leukemia.Conclusion:Among two malignant solid tumors in children, Neuroblastoma had a higher bone marrow invasion rate, while Rhabdomyosarcoma had a lower bone marrow invasion rate. Rhabdomyosarcoma can be initially divided into embryonal type and acinar type according to whether tumor cells were fused or not.