A HPLC-MS/MS method has been developed for determining Sudan I in foods. The sample was extracted by acetonitrile, and the extract after dilution was analyzed by HPLC-MS/MS. This study optimized the analysis condition. The recovery was 90.5% - 110.0%, with RSD of 1.3% -7.2%, and LOD was 10 pg. The method is fast, convenient, accurate and sensitive. The method can be used to detect Sudan I in foods.