Abstarct: Shahid Rajai Dam is constructed in 40 kilometers of south Sari on Tajan River. Study area within radius of 100 km of the Shahid Rajai dam site is including the northern and southern slopes of the eastern Alborz and part of the central Iran .in this study, the Faults are investigated in two radios of 30 and 100 kilometers around the dam site. Studies in the radius of 30 km, result to identify the faults of Mergav, Telavak, Shalmak, Majid, Vlikbon, Jurjadeh, Khoramabad and Zirab with dominant reverse mechanism, and Shokhteh-sara fault with dominant sinistral strike slip mechanism. With study of earthquake occurred in this area, focal of 11±2 km are proposed for seismognic zone. baxsed on the study of North Alborz, Khazar and Mosha faults in study area, the North Alborz and Khazar faults divided into three segment and Mosha faults divided into two segments. The evaluation of faults avoidance zone are shown that the fault rupture zone of North Alborz fault covering significant part of the reservoir of Shahid Rajai dam. Also cities of Sari, Ghaemshahr, Neka and Behshar are located in the rupture zone of Khazar fault. Fault activity classification baxsed on the fractal dimension and epicenter of earthquakes show that the North Alborz, Damghan, Badeleh, Laleband and Sokhteh-Sara faults have a high activity grade. Also according the moment and slip rates, the Damghan and Mosha fault are classified in the low slip rate and it’s expected to have a major earthquake with long return period. The results of seismic zonation potential map show that Astaneh, Firuzkoh and Mosha faults make an active seismic zone in southern part of the Shahid Rajai dam. baxsed on the deterministic seismic hazard analysis, the maximum of earthquake magnitude and acceleration are belong to segment number two of North Alborz Fault with Ms = 6.8, and horizontal and vertical acceleration of 0.48g and 0.34g, respectively. In Probabilistic seismic hazard analysis method, horizontal and vertical acceleration with return period of 100 years (equivalent to the useful life of the dam), 0.25g and 0.12g, are estimated. Also this study shows that there is good relation between the decreasing of water level and occurrence of reservoir earthquake, and these earthquakes are dominated in the south of dam site and near the North Alborz fault.