In this research, the depth variation of b-value, seismic energy released, maximum magnitude, and frequency of earthquakes in the Zagros region was studied. For this purpose, seismicity data of the region for time period 2006-2017 were analyzed. Results obtained indicate that the b-value parameter shows a decreasing trend up to depth of 15-20 km. Also, highest levels of the seismic energy released and the frequency of events are observed in depth ranges of 15-20 and 10-15 km., respectively. These observations confirm the idea that in this region the mechanical behavior of lithosphere and the pattern of accumulation and release of seismic energy, changes abruptly at the depth of about 15-20 km, which is explained by the tectonic nature of this region, as a fold-and-thrust collision zone.