Abstract: A lattice BGK model for one-dimensional unsteady open channel flows is established by analyzing the multi-scale equation s of the LB method and St.Venant equations.Some classical and practical flows,such as unsteady open channel flows in head races of hydropower plants and dam break waves,are simulated by the LB scheme.The LB results are in good agreement with the results of implicit Preissmann scheme and the method of characteristics.It is shown that the LB method is a fea sible and accurate approach to simulate one-dimensional unsteady open channel flows in engineering.