The tidal change before and after the M_S6.6(N34.5,E104.2) earthquake occurred on July 22,2013,in Minxian Gansu Province was analyzed. The tidal force was at the lowest phase point when the earthquake occurred,which indicated that the induced earthquake of the tidal force influenced by the thrust fault. According to the data of tidal cycle,the ground long-wave radiation variable condition before and after the earthquake at the epicenter and nearby area(30°~40°N,90°~110°E) was calculated based on the NOAA satellite data. The result showed that only the OLR of the epicenter and associated fractures appeared significant and continuous abnormal changing. In temporal,the change of the OLR:Initial warming→strength→peak→attenuation→earthquake→return to the normal;in spatial,the abnormal region was consistent with the north area of the North-South Seismic Belt where it was affected by the positive strain accumulation of the Wenchuan earthquake area. In the morphological evolution,the OLR changing process:scattered→conversion→scattered along the fractures,which was fully consistent with the fracturing process of the rock stress loading:initial micro-cracking→expansion rupturing →stress lockout→earthquake→normal. The active faults in the critical state maybe induced by the tidal force in this earthquake,what's more,the stress-strain process of earthquake could be characterized by the OLR anamoly.