The stress variations in the crust prior to earthquake can cause variations of geophysical and geochemical fields in the region near the epicenter. Animals have the ability to sense such variations and often exhibit some abnormal behaviors about several hours to several days before earthquake. This ability of animals have been evolved in a long period to protect themselves from natural disasters. The abnormal behaviors can be regarded as warning signals of an impending earthquake. The mechanism for the abnormal behaviors of animals earthquake is investigated in this paper. The recent research advances in life science make it possible to uncover the secrets behind abnormal animal behaviors on molecule and gene levels. The sensory system in animal may be linked to a seismic escape behavioral system and be used as a practical earthquake warning. The establishment of experimental earthquake warning system is discussed in the end.