Reservoir-triggered seismicity (RTS) is a phenomenon, which has been observed in several large dam projects all over the world, especially for the reservoirs which are constructed in seismically active regions. Practically all the territory of the Republic of Armenia is characterized as the high seismic active area. A review of reservoir triggered seismicity in Armenia shows that it mainly occurs in large dams which are located near active faults. In this paper it has been shown that the number of microearthquakes increase after Tolors reservoir operation, cause changes of seismic regime in the observed regions. The correlation of seismicity and water level in Tolors reservoir allows assuming the influence of long-term harmonious changes of water level on the seismic activity in the region.