Abstract: Nowadays in the field of animal nutrition,there is a growing interest in CLA（conjugated linoleic acid）because of its biological value,such as anticancer effects,anti-arteriosclerosis effects,improving immunity and so on.CLA mostly exist in the meat and milk from the ruminants,the CLA is the intermediate of dietary unsaturated fatty acids by rumen bacteria biohydrogenation,or comes from the dehydrogenation of monounsaturated fatty acids in the mammary tissue（lactation） and the adipose tissue（growth） through Δ9-desaturase.