Based on the "focus trigger system response" seismogenic model,the time space evolution characters of seismicity pattern before and after group strong earthquakes in Xinjiang region from 1996 to 1998 are discussed and analyzed. The signal inducing earthquake is defined. The relation between the signal inducing earthquakes and succeeding strong earthquakes is studied. The results show that the medium earthquake activity area that is triggered by strong earthquake and its border may be a dangerous region of future strong earthquake.The signal inducing earthquake within two days after the strong earthquake or its strong aftershock has forecast significance. There is a very fair possibility of strong earthquake with magnitude larger than that of the signal earthquake by 0.5~2 to occur in range of 200 km around the signal event within 3 years after the event. Finally a preliminary discussion on the mechanism of group strong earthquake activity is made.