Based on the long-term fertilization experiment station in Shenyang Agriculture University,denaturing gradient gel electrophoresis (PCR-DGGE) was used to explore the dynamics of soil physicochemical properties and the abundance and diversity of ammonia oxidizing bacteria (AOB) with seasons under different fertilization treatments,including no fertilizer (CK),low level of nitrogen (N) fertilizer (N2),high level of N fertilizer (N4) and organic fertilizer combined with inorganic N fertilizer (M2N2). The purpose of this paper is to discuss the effects of long term fertilization on the AOB and provide the theoretical foundations for rational fertilization in this region. The results showed that,compared with CK treatment,the application of organic or inorganic fertilizers increased the contents of soil ammonium N (NH4+-N) and nitrate N (NO3--N) and decreased the soil pH value. The AOB abundance of soil sampled in April was the highest among the 3 sampled time points (April,July and November). The use of inorganic N fertilizer decreased the total bacterial abundance and AOB diversity,while the organic fertilizer combined with inorganic fertilizer would contribute to the stability of soil total bacterial abundance. Redundant analysis(RDA) revealed that NH4+-N significantly affected the population diversity of AOB,and the seasonal variation played an important role in shaping AOB population structure. Generally,the seasonal variation and the long-term fertilization regime caused the changes in soil characteristics,which led to the difference in the quantity and community structure of AOB. Compared with inorganic N fertilizer,organic fertilizer combined with inorganic fertilizer would contribute to the stability of soil AOB abundance.