The abundance and community structure of total bacteria ammonia oxidizing bacteria, and archaea were investigated by real-time PCR, T-RFLP, and cloning library approaches in a wheat field under different N fertilization rates (no N fertilization, 0 kg N/hm², CK; low N fertilization rate, 75 kg N/hm², N1; moderate N fertilization rate, 150 kg N/hm², N2; high N fertilization rate, 225 kg N/hm², N3) in North China. The population sizes of total bacteria, AOB and AOA were 5.74×10⁹-7.50×10⁹, 8.89×10⁶-2.66×10⁷ and 3.83×10⁸-7.78×10⁸ copies/g dry soil, respectively. The population numbers of AOA were higher than that of AOB in all treatments, with AOA to AOB ratios ranged from 81.72 to 14.38. Significant higher numbers for AOB were detected for the high level of N fertilization soil (P < 0.05), but not in the population of total bacteria and AOA. The population numbers of AOB observed in N1, N2 and N3 were 1.64, 2.50 and 2.99 times greater than that in the CK treatment, respectively. The N fertilization rates significantly changed the communities of both AOB and AOA, and more variation was observed in the community of AOB. Phylogenetic results showed that the majority AOB sequences fell into two branches of Cluster 3, affiliated with Nitrosospira species, and all AOA sequences fell within four branches in Cluster S. Significant positive correlations were observed among the population sizes of AOB to total nitrogen and ammonium, and the population sizes of AOA to soil pH and nitrate (P < 0.05). Significant negative correlations were observed among the population sizes of AOB to soil pH and C/N ratio, and the population sizes of AOA to ammonium (P < 0.05). These results demonstrated that AOB were more sensitive than AOA to N fertilization in alkaline wheat fields in North China.