Objective　To assess the effect and toxicity of HIT2000 treatment and prognosis factors in children medulloblastoma (MB) under 3 years old. Methods　The MB patients younger than 3 years were selected and they were received HIT2000 protocol. The effect and relapse/metastasis rate, toxicity reaction during radiotherapy and chemotherapy were summarized. Prognosis factors included pathological types, molecular types, radiotherapy, tumor resection and M stage were analyzed by Kaplan-Meier and tested by Log-Rank. Results　A total of 38 patients were admitted, in which 8(21%) were completely relieved, 5(13%)were partial relieved, 6(16%) were disease stable,19(50%) were prognosis/relapse. 13(34%) patients died and 25(66%) alive. 3 or 5 years EFS rate and OS rate were 43.9±8.8% and 49.5±9.1%, respectively. The 3 or 5 years EFS rate and OS rate showed significant difference among various pathological types, molecular types and M stage (P<0.05). However, no difference was observed among groups with tumor resection, with or without radiotherapy (P>0.05). Thirteen（34%）patients received radiotherapy, none of them found with radiation encephalic necrosis and secondary tumor. One (8%) experienced radiation lung injury. All patients received chemotherapy had different grades of bone marrow suppression, and 3(7%)patients with liver dysfunction, 5(13%) with oral mucosal ulcer. Finally all damages were cured after treatment. No treatment-related deaths occurred. Conclusion　HIT2000 protocols are suitable for childhood MB younger than 3 years old, and disease prognosis are related to M stage, pathological types and molecule types, side-effect of chemotherapy and radiotherapy are endurable. This protocol can be an optional program for MB in children under 3 years old.