The paper took the 2013 Tongliao MS5. 3 earthquake as the research object and analyzed and discussed the relationship between ML4. 4 an MS5. 3 earthquakes on basis of statistical analysis of earthquake sequence and HypoDD location and focal mechanism solutions． The results showed that，the Tongliao MS5. 3 earthquake occurred with the background of longterm quiescence of medium-small earthquakes and short-term enhancement activity in epicentral area． The results of accurate seismic location showed that the Tongliao MS5． 3 earthquake sequence distributes on the NW trending，with an extension of 10km． ML ≥3. 0 aftershocks concentration occurred southern of main shock． The distance between MS5. 3 and ML4. 4 earthquakes is about 1. 8km with focal depths of 7． 208km and 7． 089km，respectively． Their focal location is very close and they might have occurred on the same fault plane． The results of focal mechanism showed that the Tongliao MS5. 3 earthquake was of a strike-slip type． Focal mechanism of aftershocks were in disorder with time lapse． The type changed from strike-slip to thrust and normal fault． The bigger foreshocks had similar focal mechanism． They were all normal fault，and to some extent exhibited a obvious crustal medium anisotropy in epicentral area before macroscopic fracture． The fracture was directional alignment with stress action enhanced，and the “consistency” of seismic precursor state would gestate the main shock． According to the characteristics of temporal-spatial distribution of earthquake sequence and similarity of focal mechanism，we judge that the Tongliao MS5. 3 earthquake is a foreshock-mainshock-aftershock type．