Three rice genotypes differing in nitrogen absorption efficiency (NAE), namely Wuyou 244 low in NAE, R832 12 medium in NAE and Shuiyuan 349 high in NAE, were planted in a pot experiment to investigate physiological and morphological characteristics of the roots of these plants growing with optimum nitrogen supply at the jointing stage, and their relat ionships with NAE. Results showed that Shuiyuan 349 was much higher than R83212 and Wuyou 244 in total length, density, surface area and dry weight of roots, and the highest in total absorption area (St), active absorption area (Sa) and ratio of Sa/St of roots, which were essential conditions for efficient nitrogen absorption. Moreover, Shuiyuan 349 was also higher in energy consumption, oxidizing capacity, reducing capacity and activities of nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase in roots, which accelerated carbohydrate synthesis and nitrogen uptake and assimilation in roots, and enhanced bleeding intensity, free amino acid and soluble sugar content in roots, thus resulting in significantly high nitrogen content and accumulation in shoots. Stepwise regression indicated that root density, root total absorption area and nitrogen content in shoots at the jointing stage were the main characters of high efficient nitrogen absorption of rice and could be regarded as reliable indicators for efficient nitrogen management and genetic improvement of rice.