To thoroughly investigate biochemical characteristics of the humic activated sludge and action mechanism, the humic biological pellets were tested by means of SEM-EDAX. The results show that the main composition elements in humic biological pellets are C, O, Si, and there are small amounts of Al, S, Fe. Compared to conventional activated sludge, the number of typical bacteria, nitrifying bacteria, nitrosobacteria, denitrifier and actinomycetes in humic activated sludge were significantly higher. Organic matter content in humic activated sludge is less than that in conventional activated sludge, but the humic acids content is higher. The humification degree of humic activated sludge is considerably higher than that of conventional activated sludge. The SBR reactor operated under humic activated sludge process performed excellent pollutant removal efficiency than conventional SBR reactor, the removal efficiency of CODCr, TN and TP is 4％, 10％ and 14％ higher respectively.