Geological and hydrological conditions of Longyangxia reservoir region are analysed.Relationship between the Gonghe M_S7.0 earthquake,1990 and water storage process of the reservoir is studied.The results show that distribution of main shock and strong aftershocks in Gonghe M_S7.0 earthquake sequence with time,changes of precursory field,deformation field and some seismometry indexes are related to the water storage process and change of water level of the reservoir,being similar to typical reservoir earthquakes.It is proved that the Gonghe M_S7.0 earthquake is induced by the Longyangxia reservoir and is an induced tectonic earthquake.