Abstract: To isolate nitrilase producing strains from soil, a rapid enzyme activity analysis method based on phenolhypochlorite colorimetry (Berthelot colorimetry) for the determination of ammonia was established. Using this method, 9 strains with relatively high nitrilase activity were obtained. The phydroxybenzonitride conversion rate of the 9 strains were also quantitatively determined by HPLC and the results of the two methods corresponded well. The highest conversion rate of one of the 9 strains was 49.9%. 16s rDNA sequence analysis showed that the 9 strains belong to genus of Chryseobacterium, Bacillus, Staphylococcus, Stenotrophomonas etc.