Hydrolysis acidification/pre-denitrification biological aerated filter was adopted in a domestic wastewater treatment plant. The effluent was accorded with a standard in the Integrated Wastewater Discharge Standard(GB18918-2002), in which the effluent phosphorus was demanded below 0.5mg/L. Although the biological treatment can greatly reduce the total phosphorus content, it still can not meet the effluent quality and also need further treatment by chemical method. This paper mainly investigates the effects of adding chemicals for phosphorus removal and effects of chemicals on the head loss, digestive reaction and the color of effluent so as to guide the practical engineering application.