Abstract: Consequences of uneconomical carbon source feeding and unstable total nitrogen in the effluent of denitrification bio-filter occur, due to great fluctuation of instantaneous inflow in an advanced wastewater treatment plant. A Guidance Table of Methanol Dosage was formulated according to the fact that actual denitrification C/N was around 7 through the historical methanol dosage and water quality data. Operators were able to query the required methanol dosing flow from this table according to the influent flow and total nitrogen data, then adjust the methanol dosage per hour in order to achieve the manual fine regulation. Influent total nitrogen was expressed as "nitrate nitrogen+constant n", which could be acquired by the nitrate meter at the total effluent of the biological aerated filter and adjustment of effluent quality online monitoring data, respectively. The value of Constant n was relatively stable at around 2. Although denitrification C/N was variable, especially increased with the decrease of total nitrogen removal, fine-regulation of methanol dosage could still be achieved by adjusting the value of constant n. Fine-regulation promoted the average total nitrogen of effluent from 5 mg/L to 8 mg/L, which could save carbon source equal to the consumption of 3 mg/L of total nitrogen, meanwhile increased the average annual effluent total nitrogen by 2 mg/L and save 1.5 million Yuan, 25% of the annual methanol cost, so as to basically achieve the equivalent effect of automatic and precise dosing. This method was simple and practical, and had certain engineering application value.