Abstract: Angiotensin converting enzyme(ACE)from pig lung was purified by DEAE ion exchange chromatography-ultrafiltration,and the DEAE ion exchange chromatography was amplified on the basis of the small-scale process. The specific activity of ACE and the recovery of enzyme activity were taken as indexes to examine the purification effect of the scale-up process and to further improve the purification conditions. The results showed that after 15 times amplification of DEAE ion exchange chromatography,the specific activity of purified ACE was(1.05±0.04)U/mg,which reached the grade of electrophoresis pure. There had no significant difference with the purification results of the small-scale process. The recovery of enzyme activity was 34.6%±0.3%,that higher than the small-scale process. This study indicated the pilot-scale of the purification was feasible and could greatly increase the purification efficiency. The process would provide a foundation for a larger scale of ACE purification.