Entropy is an important concept both in natural and social sciences._x000D_
Considering the preparatory process of the earthquakes as an open system, in view of basic ideas of the Theory of the Dissipative Structure, the seis- mological Entropy is introduced as an order parame- ter, describing the scale of order associated with the earthquake distribution in time, space and mag- nitude. The features of evolution of seismic acti- vities before and after the large earthquakes have been studied by using the seismological entropy._x000D_
The preliminary results show that the seismological entropy in certain region decreases as the large earthquake is approaching, it means that the distri- bution of earthquakes has turned gradually in order from disorder._x000D_
It is expectation that the application of the Principle of Entropy in seismological research will deepen the understanding of the physical process of earthquake preparation. Meanwhile, it will also offer some enlightements in studying mitigation of seismic hazard as well as earthquake prediction.