Dez flow dam Site has located on Zagros folded belt. Khalaj, Pirahmad and Dezfol faults are the most important seismic sources in this area and they should be considered accurately. Khalaj fault is a capable to generation of big earthquakes (M>7). Maximum horizontal and vertical acceleration of Predictable earthquake on this fault is 0.697g and 0.618g respectively by deterministic approach. Also, according to probabilistic approach, maximum horizontal acceleration for 150, 475 and 2000 years repeat times are 0, 234g, 0.273g and 0.331g respectively.