Abstract: Objective　To clarify the characteristics and clinical significance of the NOTCH1 mutations in childhood T-cell acute lymphoblastic leukemia (T-ALL). Methods　Amplify and sequence the heterodimerization (HD) domain and the proline- glutamicacid-serine-threonine (PEST) domain of the NOTCH1 gene in 28 T-ALL children, in order to explore the frequency, position and type of the mutations as well as their reletions with prognosis. Results　In 28 children with T-ALL, 15 cases (51.57%) had been identified the NOTCH1 mutations, all of which were heterozygous mutations. The lymphoblast counts in peripheral blood and bone marrow in the NOTCH1 mutant group at admission were significantly higher than in the non-mutant group (P<0.05). The 1-year remission rate in the 28 children with T-ALL was 75% (21/28), including 80% (12/15) in mutant group in which 3 patients relapsed and all of them died (1-year mortality 20%) and 69.20% (9/13) in non-mutant group in which 4 patients relapsed but all survived (1-year mortality 0%). Conclusions　The children with T-ALL had a high incidence of NOTCH1 mutations at various sites. In addition, the patients with NOTCH1 mutations had more severe disease at diagnosis, better short-term prognosis and poor outcome with salvage therapy after relapse.