This study was purposed to investigate the methylation status of id4 gene promoter in patients with chronic myeloid leukemia (CML) and explore the relationship between methylation of the id4 gene and progress of CML. The methylation status of id4 gene in 48 chronic myeloid leukemia patients and 10 healthy individuals was detected by using methylation-specific polymerase chain reaction (MS-PCR). The results showed that id4 gene was unmethylated in bone marrow samples from both healthy individuals and CML patients in chronic phase (CP). The rate of id4 gene methylation in both CML patients in accelerated phase (AP) and blast crisis (BC) was 66%, and was higher than those of CML patients in CP phase. There was significant difference between them (p < 0.05). In one CML patient who received a serial observations, the status of id4 was unmethylated in CP, but it was methylated in AP and BC phase. It is concluded that the id4 gene in CML patients is unmethylated in CP, while it is methylated in AP or BC. The detection of id4 gene methylation status may be useful for monitoring disease advance in CML and may be used as a marker of disease progression in CML.