Nitriifcation inhibitors, such as dicyandiamide (DCD), have been shown to decrease leaching from urea- and ammonium-based fertilizers in agricultural soils. The effect of nitriifcation inhibitors on nitriifer and denitriifer in short-and long-term intensive vegetable cultivation soils was poorly understood. In this study, the pot trial was conducted to investigate the differential responses of nitriifer (amoA-containing bacteria) and denitriifer (nirK-containing bacteria) to DCD in short-(soil S) and long-term (soil L) intensive vegetable cultivation soils. Quantitative polymerase chain reaction (qPCR) and terminal restriction fragment length polymorphism (T-RFLP) were employed to detect the abundance and composition of amoA-and nirK-containing communities. The results indicated that application of DCD led to a consistently higher NH4+-N concentration during the whole incubation in soil L, while it was quickly decreased in soil S after 21 days. Furthermore, DCD induced more severe decrease of the abundance of amoA-containing bacteria in soil L than in soil S. However, the abundance of the nirK-containing community was not signiifcantly affected by DCD in both soils. Long-term vegetable cultivation resulted in a super-dominant amoA-containing bacteria group and less divergence in soil L compared with soil S, and DCD did not cause obvious shifts of the composition of ammonia-oxidising bacteria (AOB). On the contrary, both amoA-and nirK-containing bacterial compositions were inlfuenced by DCD in soil S. The results suggested that long-term intensive vegetable cultivation with heavy nitrogen fertilization resulted in signiifcant shifts of AOB community, and this community was sensitive to DCD, but denitriifers were not clearly affected by DCD.