The activated sludge was acclimated by the inorganic salt medium containing phenol as the sole carbon source. The phenol-degrading bacterium obtained now can degrade completely phenol at initial concentration of 1 700mg/L at 30 for 15h, and COD can be degraded by 96.9%. Some factors effecting degradation of phenol and COD were studied, which include initial phenol concentration, quantity of bacterium, temperature and pH. Four strains of bacterium were isolated from the mixed phenol-degrading bacterium. It is shown that the degradation effect of mixed bacterium is superior to that of sole strain.