Abstract: Because of the autonomous mobile sensor nodes which make the network unavailable to sustain stable connectivity, permanently, wireless mobile sensor network is separated into many local subnets persistently. Based on the in-depth study on the dynamic separation of the network, the reasons why the net separation has to be done are analyzed in view of physics and links. Defining the net separating time ratio, degree of net separation and loading rate of network, the net separation is discussed quantitatively. Lots of simulative data revealed that there are two features of the net separation, i.e., the net separating time ratio is inversely proportional to the number of nodes and the loading rate is directly proportional to the stability of the degree of net separation. The results of the study will provide a reference for not only the application of wireless mobile sensor networks but also the study on upper layer protocols.