Degradation of phenol and 4-chlorophenol by Pseudomonas putida LY1 was studied. It was found that phenol can be effectively degraded by the bacteria with an optimum phenol concentration at 50 mg·L^-1. Inhibition of the bacteria increased with the 4-chlorophenol concentration. A modified Haldane equation was used to study the biodegradation of phenol by Pseudomonas putida LY1. The equation parameters calculated using MATLAB software were as follows: R_m=0.113 mg·mg^-1·h^-1, K_s =3.5 mg·L^-1 and K_p =126.6 mg·L^-1. The modified Haldane equation was also used to simulate the cometabolic biodegradation of phenol and 4-chlorophenol by Pseudomonas putida LY1. The cometabolic degradation model can simulate the process of cometabolic degradation very well. The model provides a theoretical and technical reference for the biodegradation of chlorinated refractory organic pollutants in wastewater treatment plants.