Significant difference of nitrification can be always found between rices different in cultivar, which may result in difference in nitrogen use efficiency between the two rice cultivars. A rhizobox with three compartments and subsequent soil-slicing was used to determine simultaneously variation of nitrification and ammonia oxidizing bacteria (AOB) in the rhizospheric soils of two rice cultivars, i.e. Shanyou 63 (Indica) and Wuyun 7 (Japonica), growing at an N level of 30 mg kg^-1 soil ^-1. Composition of AOB communities in the rhizosphere was studied by means of DGGE (denaturing gradient gel electrophoresis) of 16S rDNA of the AOB. Results show that nitrification activities of both rice cultivars increased with the incubation time. Peak nitrification activities were found in rhizospheric soil. In the rhizosphere nitrification activities decreased with the distance from the root. The maximum nitrification activity was measured to be at 0.77 mg kg ^-1 h^-1 and 0.73 mg kg ^-1 h ^-1, in Shanyou and Wuyun respectively. The populations of AOB in the root zone, rhizosphere (0～4 mm away from the root zone) and bulk soil (>4 mm away from the root zone) for both rice cultivars increased during the growth periods The composition of AOB communities in the rhizosphere of Shanyou 63 is more abundant than of Wuyuny 7, showing that Indica might have a stronger nitrification in rhizosphere and on root surface and hence have a higher capability of utilizing nitrate than Japonica.