Abstract: Changes in functional properties of biological denitrification in the long-term use of methanol were explored,with addition of methanol(ρ_(TOC)/ρ_(N)=1.6±0.2) at the start of anoxic phase in sequencing batch reactor(SBR).The results showed that stable nitrate reduction rates were not reached until 37 days of methanol addition,and specific denitrification rate increased from 0.378 mgNO_x-N/(gVSS·h) to 2.406 mgNO_x-N/(gVSS·h).Besides,from nitrogen uptake rate(NUR) tests with methanol acclimation sludge,the appropriate range of ρ_(TOC)/ρ_(N) ratios for complete denitrification was 1.10-2.68.However,the temperature coefficient of 16 ℃ to 20 ℃ was calculated to be 1.07,which indicated that temperature decrease exerted a great inhibitory effect on biological denitrification.For economic reason,the addition of methanol should be adjusted to biological microenvironment and ambient environment.