The acid protease is stated as follows: 1. Product character:solid,tawny powder. 2. Working means:Act on peptide linkage of protease,main result are peptides and amino acid. 3. Hot stability:in the case of PH:2.0-4.0, it is stable below 40 centi degree,and the enzyme activity will be damaged seriously over 50centi degree,and it will lost activity fast over 60 centi degree. 4. PH stability:stable value:2.0-2.4 5. Working condition:temperature range:40-50centi degree;the best temperature:55centi degree;working range of PH:2.5-5.5,best value:PH3.0-3.5. 6. Effect that metal impose on enzyme activity:it can be activated by Ca,Mg,and it is controled by Cu, mercury,Pb.