A method for preparing biospecific affinity chromatography agarose for angiotensin-converting enzyme is reported. Bisoxiranes, 1,4-butanediol diglycidyl ether, has been used for introducing reactive oxirane groups into Sepharose CL-4B, and coupling to ACE selective inhibitor——lisinopril in anion conditions including NaBH as deoxidizer. 0.79 mg ACE protein was purified from 200 g hog lung homogenate by 1.6～2.6 mol/L ammonium sulfate fractionation, dialysis, buffer balance and affinity chromatography. The recovery of ACE activity was 11.9% with specific activity of 38.8 U/mg protein and the enzyme was purified 808 fold in comparison with the homogenate supernatant of hog lungs, specially, only one step of affinity chromatography, the enzyme was purified 264 fold. Purified ACE showed a single band after migrated identically in sodium dodecyl sulphate-polyacrylamide gel electrophoresis and given an apparent molecular mass about 180 ku.