The degradation performance of six volatile organic compounds (VOCs), toluene, o-xylene, m-xylene, p-xylene, benzene and chlorobenzene by activated sludge acclimated with toluene were studied. The experimental results showed that the biodegradation rates of o-xylene, m-xylene, p-xylene, benzene and chlorobenzene increased with increasing of their initial liquid concentration; when concentrations of o-xylene, m-xylene, p-xylene, benzene and chlorobenzene were less than 149 mg/L, 129 mg/L, 133 mg/L, 234 mg/L and 146 mg/L respectively, neither of them brought any notable inhibition or poisonous effects on microbes, and their aerobic biodegradation accorded with first-order reaction. When concentrations of toluene were more than 85 mg/L, its biodegradation rate didn't increase with increasing of its initial liquid concentration and the biodegradation of toluene accorded with the Monod equation.