Why do hillslopes appear the current form Why do river channels branch? Hydrologists and geomorphologists have studied these problems for a long time. And they have found some common controlling principles. Now they also concentrate on the studies of hydrologic processes which were ignored on their earlier researches. The purpose of this paper is to discuss the model of river basin evolution. We proposed the concept of channel initiation threshold and considered the influences of erosional resistance, slope and runoff mechanism. We also combined hydrologic processes and drainage density through these properties of catchment.