In this paper,a new dispersive wave real-time forecast method is presented,which describes law of flood wave motion in natural channel by dispersive wave equation,combines river channel flow routing with mathematics physics inverse problem theory and discrete inverse method.Its particular is that flow rate Q(x,t),dispersive wave velocity C(x,t)and diffusion coefficient D(x,t)are calculated in the same time.The real-time updating technique of parameters and forecast process is based on some new information acquired by monitoring.