The invention discloses a method for rapidly detecting the activity of nitrilase. The method comprises the following steps: adding hydroxylamine hydrochloride and an ethanol solution of dicyclohexylcarbodiimide into a nitrilase reaction sample, vibrating the mixture to evenly mixing the solution, heating the solution by a water bath, then adding an ethanol solution of iron trichloride, fully carrying out color development, measuring the absorbance value at 520 nm by a ultraviolet spectrophotometer, and calculating the activity of nitrilase according to the absorbance value; the measured relative standard deviation (RSD) and recovery rate are 1-2% and 99-102%, and the results are identical with those of HPLC method. The provided method has the advantages of simpleness, rapidness, safety, cheapness, and precision, and can be applied to rapid screening and high flux screening of nitrilase.