The aim of the study is to obtain an efficient expression of recombinant ubiquitin-like specific protease 1 (Ulp1) by gene engineering. We cloned the Ulp1p, active fragment (403 aa-621 aa) of Ulp1, from Saccharomyces cerevisia, and subcloned into pGEX/Rosetta (DE3) to form an expression plasmid, pGEX-Ulp1p-His6. In order to enhance the solubility of GST-Ulp1p-His6, we purified the fusion protein GST-Ulp1p-His6 by either glutathione S-transferase agarose or Ni-NTA resin chromatography, the purity was up to 98%. We utilized the protein to cleave the SUMO fusions, and the specific activity of GST-Ulp1p-His6 was 1.375 x 10(4) U/mg. This study showed that the recombinant protein GST-Ulp1p-His6 displayed high specificity and activity.