Abstract: Two strains of bacteria(W1 and W2)feeding only on 2-chlorobenzoic acid were isolated.The degradation enzyme system of W1 is inducible,with rate constant being -0.134 h ^-1,whereas the degradation enzyme system of W2 constructive with rate constant being -0.038 8 h ^-1 while degrading 2-chlorobenzoic acid.Besides,W1 can also degrade 4-chlorobenzoic acid,benzene,toluene and 2-hydroxphenol,but not 3-chlorobenzoic acid,1,4-dichlorobenzoic acid,ethylbenzene,propylbenzene and naphthalene. Plasmid and chromosome extraction experiments indicate that the degradation genes of W1 are on chromosome.