Objective To determine the content of trans fatty acicls in foodstuff sold in Yantai by GC-MS/MS to provide references for people arranging their diet. Methods Fatty acids extracted from foods were hydrolyzed with KOH-CH30H; the fatty acid methyl esters were then injected into and analyzed by GC MS/MS and quantified with external standards. Results Trans fatty acids were widely existed in greasy food solcl in most of markets and supermarkets. Conclusion The quality of greasy food was irregular, and the content of trans fatty acids were different. It is suggested for residents that more attention should be paid to the ingredient on the label of food products while shopping