The aim of the research was to find the up-regulated microRNA (miRNA) in K562 cells treated by 5-aza, to detect the miRNA expression in healthy people, CML patients and leukemia cell lines and to investigate the influence of miRNA on K562 cell proliferation. Up-regulated miRNA in K562 cells after 5-aza treatment was screened by microarray. The up-regulated miR-638, miR-663 and miR-92b with CpG islands in upstream region were screened by microarray in combination with bioinformatics. The miRNA mentioned above was further ascertained by SYBR-green real-time PCR. Up-regulated miR-663 was confirmed by real-time PCR. Expression level of miR-663 was detected in K562, U937 and Kasumi cell lines, and white blood cells from bone marrow of normal donor and from peripheral blood of newly diagnosed CML patient. Methylation-specific PCR (MSP) was applied to analyze the methylated status of miR-663 CpG island in K562 cells. Proliferation of K562 cells was observed after miR-663 was over expressed by transient transfection. The results showed that the expression level of miR-663 in K562 cells was up-regulated after 5-aza treatment, and the expressions of miR-663 were lower in K562, U937, Kasumi cell lines and newly diagnosed patients, compared with healthy people. The CpG island of miR-663 was methylated in K562 cell line according to detection result of MSP. The proliferation of K562 cell could be suppressed by over-expression of miR-663 in vitro. It is concluded that miR-663 CpG island is methylated in K562 cell line. The miR-663 is down-regulated in K562, U937, Kasumi cell lines and CML patients, compared with healthy people. miRNA-663 in K562 cells is up-regulated after 5-aza treatment. Over-expression of miR-663 can suppress the proliferation of K562 cells, which suggests that miR-663 may possesses suppressive effect for leukaemia.