Abstract: With A.davidianus pepsin as raw materials, extraction and purification of pepsin from stomach of A.davidianus were studied.Pepsin was isolated by extraction with PBS buffer, precipitation with 80% saturation ammonium sulfate, ion-exchange on DEAE-52 cellulose, gel filtration on Sephadex G-100 and HPLC.Finally the gotten pepsin was purified 239.87 times.The recovery rate was 4.4%.The pepsin was estimated to be 31ku with SDS-PAGE.The optimal temperature for pepsin activity was 40℃, lower than 40℃ the pepsin was stable, when the temperature raised, the activity decreased rapidly.The optimum pH was 2, the activity was stable in the pH range of 2 ~ 6.Further studies showed that the activity was rapidly decreased by EDTA, BrAc, NBS.Using casein as substrate, under the pH2.0, 40℃, Km was 7.3×103mg/L, Vmax was 2.674μg/min.