Apolipoprotein AI(apo AI) was separated and purified from human serum by precipitation with dextran sulphate 500(DS 500), density gradient zonal ultracentrifugation,delipidation and Sephadex G150 gel permeation chromatography.Identifying by SDS-posyacrylamide gel electrophoresis (SDS-PAGE)and analytical islelectric focusing (IEF),the purified apo AI shows only one band on SDS-PAGE, and the molecular weight is 28 180. With DS 500 sedimentation,this method saves time for ultracentrifugation,which is much valuable for large-amount purification of apo AI.