Human breast cancer cell line MCF-7 and its sub-clone LM-MCF-7 with high metastatic potential supply a cell model for studying molecular mechanisms of tumor metastasis. The two cell lines were used to screen tumor metastasis-associated genes by cDNA microarray, displaying differential gene expression profile. Total RNA of the two cells was extracted and the cDNAs were labeled with Cy5-dCTP and Cy3-dCTP, respectively. Then the cDNAs were hybridized on the gene chips containing 21 329 kinds of human genes. The signals were examined by GenePix Pro 4.0 software. The two labeling nucleic fluorescent dyes were exchanged each other so that the experiments were repeated twice. The results shown that 67 kinds of genes were markedly different between the two cells, in which 41 were up-regulated and 26 down-regulated in LM-MCF-7 cells. Some of results were confirmed by real-time PCR. The above genes are associated with functions, such as cell signal transduction, transcript regulation, transportation, response to stress, metabolism, development, movement, cell cycle, differentiation, apoptosis, conglutination, and so on. According to the reports 35 of 67 genes were involved in tumor, in which 9 were related to metastasis of breast tumor, and 6 may be involved in tumor invasion and metastasis. Based on the results, apoptosis was investigated in function in LM-MCF-7 and MCF-7 cells. It was found that the ability of antiapoptosis in LM-MCF-7 cells was higher than that in MCF-7 cells. The candidate genes associated with tumor metastasis will be further demonstrated in function.