In this paper, the process of the present deformation and rupture in the inhomogeneous earth's crust, the system of precursors and the precursor of the rupture, the zones of the strong seismic ruptures and the nefworks of ruptures in the crust of China's continent have been discussed. It has been believed that a process of a big eacthquake, which is not insulary, is a part of the system of quick rupture of tectonic activity from which a large a mount of elastic energy is veleased, The frame of the network of strong seismic ruptures mostly depends on the inhomogeneous strength of the earth's crust. But the form, major direction and the tendency of regional rupture mostly depend on the variety of field stresses. Thus, the seismlc activity and precursors should possess the properties of the network and system. The study of these problems is of great signifcame to the analysis of seismic activilies and precursors.