Abstract: Abstract: Human TNFAIP1(originally termed B12) was first identified as a tumor necrosis factor α(TNF-α) and interleukin-6(IL-6) inducible protein. Experiments on human and rat suggested the protein may play roles in the DNA repair, DNA synthesis, cell apoptosis and human diseases. But its real function and mechanism has not been reported. In this paper, human TNFAIP1 was cloned and the GST fusion protein was expressed in the bacterial BL21.The expression of TNFAIP1 was determined in a number of cell lines by Real-time PCR. We found that the expression levels of TNFAIP1 are high in COS7 and NIH3T3 cell lines but low in the cancer cell lines. These suggest that TNFAIP1 may be involved in the process of cancer.