Analysis of the formation of a dynamic membrane (DM) was conducted in detail; based on a great deal of experiments, a practical model was proposed to characterize the formation process of the dynamic membrane. In order to validate the model, the following experiments were done: effects of crossvelocity and transmembrane pressure on the formation process of DM were examined with kaolins of 1,250 mesh and 6,000 mesh as DM materials respectively. The experimental results showed that the experimental values approached the theoretical values in steady state and unsteady state when the system constant of k0 was 2 and 10 respectively. But differently from the model, the filtrate flux was still declining with time in the steady state.