Nitrogen leaching is an important pathway of nitrogen (N) loss from paddy fields to surrounding water, contributing nitrate pollution to groundwater. Different methods have been employed to study N leaching. In order to provide science and technology supports for study on nitrogen leaching, a summary of various study methods and their advantages or disadvantages were presented in this paper, including soil solution extractor, monolith lysimeter, soil drilling and sampling, computer models methods and stable isotope techniques, and the calculation of the nitrogen leaching, including water balance method, Darcy law method, small lysimeter method and large-scale monolish lysimeter method were also concluded in this paper.