This paper studied the biomass maintaining method of Ozone Biological Activated Carbon(O₃-BAC)process when intermittent operation was conducted as well as the influence of different storage way on the purifying effect of O₃-BAC process rerunning. The results shows that when storage with immersion was implemented after O₃-BAC process stopped, water quality in the activated carbon layer has changed a lot, and biomass was decreasing. In the meantime, periodic water replacement could delay the decline of biomass when the activated carbon column was immersed in storage. When the O₃-BAC process was rerun, the decline of biomassbrought about by the periodic water replacement had little influence on the removal efficiency of turbidity and UV₂₅₄, but this operation could make the removal efficiency of COD_Mn and ammonia nitrogen by the O₃-BAC in a short time close to the same of the process before storage.