Abstract: Pig femoral collagen enzymatic hydrolysate was pretreatmented by 0.22μm and 0.45μm microfiltration membranes,then used the MWCO 5,3,2ku ultrafiltration membrane for ultrafiltration step by step,and the color value,clarity,protein recovery and ACE inhibitory as index,the effect of the different permeate on enzymatic hydrolysate were compared,taken the test to remain activity under acid,alkaline conditions,hot environment and trypsinl enzymes proteolysis.The results showed: the enzymatic hydrolysate was pretreatmented by 0.22μm better than 0.45μm in color value and clarity,but the former was lower in protein recovery,they had no difference in ACE inhibitory.All of the permeate were obtained and the MW < 2ku had the best activity with the IC50 was 0.83 mg/m L.The stability of antihypertensive peptide,lower than 2ku,was investigated and the results this kind of peptide could remain activity under acid,alkaline conditions and hot environment could had the ability to resist trypsinl enzymes proteolysis.However,the activity decreased when treated by pepsin,and it's activity keep more than 95% of the original.