Reservoir sedimentation is a serious problem to gradually lose normal function of a reservoir. Lateral erosion in reservoir flushing technologies is a kind of very good method to flush reservoir sediment deposition. In the past, the method was not summarized systematically. On the basis of the experience and data obtained by the method in the Toutunhe Reservoir in 2001, and through analysis, an empirical formula was given. At the same time, according to the reservoir characteristics of lateral flushing and regularity, with a pipe flushing, a simple formula used for controlly flushing discharge and several operational methods were proposed. This research result is not only beneficial to the Toutunhe Reservoir management, but also provides the theory basis of applying lateral flushing in reservoir for other similar reservoirs.