Abstract: 　Objective　To explore the expression and clinical significance of microRNA-200a in childhood B-cell acute lymphoblastic leukemia (ALL). Methods　Bone marrow samples were collected from 45 children with B-cell ALL and 18 children without hematology disease as control. Total RNA was acquired from bone marrow. qRT-PCR was performed to detect the expression level of miR-200a. Results　The relative expression level of miR-200a in B-cell ALL group was significantly lower than that in control group (p<0.05); the expression of miR-200a in children over 10 years old was significantly lower than those in children under 10 years old (p<0.05); the expression of miR-200a in newly diagnosed samples was lower than those in those samples taken on Day 33 and at Week 12, respectively (p<0.05, p<0.01). In addition, the expression of miR-200a in low-risk group was higher than those in mid-risk and high-risk group, respectively (p<0.05). Conclusions　Low level of miR-200a had a close correlation with the development and prognosis of childhood B cell ALL, which could be used as a potential target of therapy and a biomarker of childhood B cell ALL in the future.