The diverse effects of different sources of trans fatty acids on human health have been reported. Therefore， the objective of this study was to investigate the composition and content of trans C16：1， trans C18：1， trans C18：2 and CLA isomers in food， and provide scientific theory for studying the relationship between trans fatty acids， CLA and heath in different foods. Determination of trans C16：1， trans C18：1， trans C18：2 and CLA isomers in ruminant animal fat， edible oils and frying oils by combining silver ion solid phase extraction column and the two heating programs of gas chromatography. Result showed that 23 trans fatty acids were detected in the sample， of which 7 were trans C16：1， 10 trans C18：1， 6 trans C18：2 and 6 were CLA isomers. The trans C16：1， trans C18：1 and CLA in ruminant fats were significantly higher than those in edible oils and frying oils， while the trans C18：2 content in frying oils was higher. 9t C16：1，11t C18：1 and 9t12t C18：2 were the main trans fatty acid isomers in ruminant animal fat， and the main CLA isomer was 10t12c CLA， while 12t C16：1， 9t C18：1， 9c12t C18：2 and 9t12c C18：2 are the main trans fatty acid isomers in edible oil and frying oil， and the main isomers of CLA were 10t12c CLA and 11c13t CLA. Comparing edible oil edible and frying oil， the fatty acid composition of camellia oil had the smallest change， while the content of trans C18：2 and trans C18：1 in most frying oils significantly increased compared with those in unfried oils. It can be seen that the major trans fatty acid isomers in ruminant animal fat， edible oil， and frying oil are different， while the effects of different isomer fatty acids on human health are diverse. Camellia oil is suitable for frying， and edible oil rich in polyunsaturated fatty acids will produce more trans C18：2 after frying， which has greater potential for human health than trans C18：1， therefore， the control of frying oil quality should be paid great attention.