In this study, two rice cultivars, Wuyunjing7 (Al-tolerant) and Yangdao6 (Al-sensitive), as experimental materials in rice hydroponic experiments were selected to investigate the effects of different N forms on Al toxicity through long-term and short-term treatment. Results showed that compared with NH4+, NO3- increased Al uptake by rice, Al content in root increased significantly with the increase of NO3- concentration but decreased significantly with the increase of NH4+ concentration. These results showed that the effects of NH4+ and NO3- on Al uptake by rice had a concentration-effect. When pH buffer was used, the difference in Al accumulation in root decreased between NH4+ and NO3- supply, which demonstrated that the difference in pH values of the NH4+ and NO3- solution may be the reason for the different Al contents of roots under NH4+ and NO3- supply.