Soybean is an indispensable protein source in the rations of poultry and livestock. However, unprocessed whole soybean cannot be directly utilized in the feed due to the presence of various anti-nutritional compounds which reduce animal weight gain. Among them, trypsin inhibitor is the most dominant antinutritional compound. Rapid and accurate measurement of trypsin inhibitor will be critical for soy processors to assess the quality of soy meal used in the animal feed. Currently, trypsin inhibitor activity is measured utilizing the “standard method” that has been approved by American Oil Chemists Society (Method Ba 12-75) and American Association of Cereal Chemists International (Method 22-40.01). We have modified and improved this “standard method” resulting in the elimination of several time-consuming steps and drastically reducing the assay volume from 10 to 1 ml. The proposed 1 ml assay is easy to perform, uses less reagents, more sensitive and reliable. By employing this rapid assay, we have measured trypsin inhibitor activity of hundreds of soybean meal samples obtained from industry partners. Moreover, our rapid assay can also be carried out in 96-well microplates which will enable high-throughput screening of large number of soy meal samples.