The invention relates to a method for determining the amount of oat flour addition in compound flours and noodles, and it belongs to the field of food detection technology. Based on the similarity of the fatty acid composition between oat and wheat, the quantitative analysis index used for measuring the oat flour addition was determined. Based on the differences of fatty acid contents in oat and wheat, the relationship between the changing trend of fatty acid composition and oat flour content in compound powders or noodles is employed to quantitatively determine the amount of oat added to these compound flours or noodles. The invention provides a highly sensitive and feasible method for safety monitoring and quality control of oat flours and oat noodles.