Chloro- and nitro- substituted aromatics are toxic and persistent in the environment. Pseudomonas putida ZWL73, isolated from 4-chloronitrobenzene (4CNB) polluted soil, can grow on 4CNB as carbon and nitrogen sources. Enzymatic analyses were carried out in order to illuminate the degradation pathway. Two key enzymatic acivities were found to be invovled in the degradation: the nitroreductase activity that catalyzing the first step and the ring-cleavage dioxygenase activity leading the substrate to be mineralized. The degradation was therefore decided to process through a partial reductive pathway together with the proofs of the results of degradation intermediates test and growth substrate test.