Abstract: Objective To investigate the clinical significance and mechanism of Fhit gene abnormal expression in leukemia. Methods Bone marrows from 117 cases with leukemia patients and 28 normal cases(as control) were collected.The level of Fhit transcripts in leukemia patients and control cases were assayed using reverse transcriptase-polymerase chain reaction (RT-PCR),Methylation PCR (MSP) were used to detect the promoter methylation of Fhit gene.The relationship between the expression of Fhit mRNA and abnomal methylation of Fhit gene with clinical data the same as the correlationship between the methylation of Fhit gene with the expression of Fhit mRNA was analyzed. Results In 117 cases,there were 57 cases (48.72%) expression of Fhit mRNA.In control group,the ratio of Fhit gene expression was 96.43%(27/28) and no methylation of Fhit gene was found. There was significant difference between the expression of Fhit mRNA in leukemia group and control cases group the same as the methylation prevalence of Fhit gene (P<0.05).Compared the relationship between the expression of Fhit mRNA and abnormal methylation of Fhit gene with clinical data,they were different in immature leukemia cells the same as in liver and spleen or lymph node (P<0.05). Conclusion The abnormal methylation of Fhit gene may be the major mechanism of gene silence in leukemia,resulting to be no expression of Fhit mRNA,and the abnormal methylation of Fhit gene maybe relevant with the process of occurrence and development in the leukemia.There also maybe some effective and significant in the process of diagnosis and curative effect of leukemia patients by detecting the methylation status of Fhit gene.