Abstract: This paper describes the changes of soil nitrification affected by three allelochemicals--benzoic acid，p-hydroxybenzoic acid and ferulic acid in different concentrations．soil moisture content and pH．The contents of NO₃^--N were determined at l day，4 days，7 days，10 days and 14 days after the soil treated The results showed that inhibiting rates of ferulic and benzoic acids were higher than that of P-hydroxy benzoic acid on nitrification and the inhibiting effects of ferulic acid increased with the increase of allelochemical concentration．The soils with different pH didn’t show obvious difference in nitrification，because these soils were all close neutrality．The water content of soil affected total N0₃^--N．The normal soil samples inverted a few of N0₃^--N，while the inverting content of the water saturated soil samples increased with time．It indicates that the water content of soil is very important for nitrification．