The amino acid sequence (1-301aa) coding the human PTP1B catalytic domain (PTP1Bc) was obtained from the GenBank. The PTP1Bc gene was constructed by overlapping PCR, then was inserted into vector pET-22b(+) and expressed efficiently in E. coli BL21(DE3) under optimum condition after IPTG induction. The proteins were expressed mainly as inclusion bodies with the yield of more than 30% of total bacterial proteins. The expressed products were purified through Ni2+-affinity chromatographic column. After purification, the purity of the proteins was more than 95%. Western blotting analysis suggested that the purified proteins could specially combine with anti-PTP1B antibody. Enzyme activity assay showed that the protein has phosphatase activities.