Abstract: UV-spectrophotometry was applied to the measurement of trypsin inhibitor activity of soya-bean products,based on the inhibitory effect of trypsin inhibitors on the catalytic action of trypsin on the hydrolysis of benzoyl-dl-arginine-p-nitroanilide hydrochloride (BAPA),the product of which showed an UV-absorption at 410 nm.The magnitude of the decrease of absorbance at 410 nm is a measure of trypsin inhibitor activity.The proposed method was checked for its feasibility and accuracy by standard sample of soyabean containing trypsin inhibitor,giving value of RSD′s (n=10) of 3.0%.In analyzing a substantial soya-bean sample for 10 determinations,an average value of TIU/g obtained was 2 527,with a RSD value of 1.2%.