A pectinesterase produced by Aspergillus niger SL2-111 was isolated and purified by three steps including ammonium sulfate precipitation,DEAE Sepharose Fast Flow ion exchang-e and Sephacryl S-200 filtration chromatography.The electrophoretically homogeneous pectineste-rase was obtained with its molecular weight estimated 48.8 ku on SDS-PAGE.Optimal pH and temperature were 5.8 and 60℃,respectively.Its activity maintained relatively stable under such conditions as temperature below 50℃ and pH value between 5.8-6.2.