Abstract: Objective：To investigate the possible role of Notch signaling pathway in the development of human acute B cell lymphoblastic leukemia. Methods：Real-time quantitative RT-PCR was applied to detect the mRNA levels of Notch signaling genes including Notch1,Notch2,Jagged1,Delta1,Hes1 with GAPDH as the internal control, in the bone marrow from 16 B-ALL patients at diagnose（the blast plus prolymphocytes over 80%）and 11 normal controls by using a ABI PRISM 7700 thermal amplifier. The mRNA expression level of Notch was normalized as a ratio between the PCR values of Notch and GAPDH times 106. Results：The mean value of mRNA levels of Jagged1in 16 B-ALL at diagnose was significantly lower than those of control group［(76.7±23.8) vs. (2192.3±971.6), P=0.000］, while the mean value of mRNA level of Delta1in 16 B-ALL at diagnose was statistically higher than those of control group ［(60316.6±8713.5) vs. (2189.8±802.3), P=0.002］. However， The mean mRNA expression levels of Notch1,Notch2 and Hes1in B-ALL group at diagnose ［(6167.6±1661.3)， (95318.6±9437.5) and (258.2±96.2) respectively］ compared with those in normal control group ［(1735.5±936.6)， (52078.2±8746.3) and (1006.2±806.0) respectively］showed no statistic difference between these two groups (P= 0.089, 0.815 and 0.786 respectively). Conclusion：The mRNA level of Jagged1was dramatically less while Delta1 was evidently higher in B-ALL patients compared with those in normal control group, suggesting the aberrant expression of Jagged1 and Delta1in Notch signaling pathway may contribute to the development of human acute lymphoblastic leukemia.