Abstract: The m-cresol degrading composite strains were isolated from the aerobic sludge of coking wastewater of Guangdong SGIS Co. Ltd.，and were named CDMs (cresol degrading micro-organisms) according to their function. In shaking flasks experiments，the effects of degradation conditions were studied and the optimum pH，inoculums amount，temperature and concentration of metal ions usually present in wastewater were determined. At pH 6.2~7.2，inoculums amount 10%~15% and temperature 35~40 ℃，the degradation of m-cresol was efficient. The presence of K+，Na+，Ca2+，Fe3+ and Mg2+ ions could improve the biodegradation ability when they were 50 mg/L，2000 mg/L，3 mg/L，1.5 mg/L and 4~10 mg/L respectively while the presence of Cu2+ ion could restrain the reaction seriously. Under specified conditions，the degradation with different initial concentrations exhibited first order kinetics characteristics. When the initial concentration was 551 mg/L，the average degradation rate reached a maximum，8.4 mg/ (L·h)，and the composite strains were the most efficient and toxicity-resistant for m-cresol degradation.