Iran is a very seismic pressure zone due to its location in the Alpine-Himalayan seismic belt and the convergence zone of Arabian and Eurasian plates, as well as the presence of numerous faults. Therefore, seismic hazard analysis is always important for this country to minimize the damage caused by this natural disaster. Investigating a relationship between intensity and magnitude to investigate the magnitude of historical earthquakes and the immediate outcome of the damage caused by future earthquakes has been noticed in seismic risk analysis. In this study, by updating the intensity-magnitude catalog for earthquakes with magnitudes greater than 5.5 MW by the end of 2021 in Iran, a new relationship for intensity-magnitude conversion is presented. The resulting relationship also compared with several relationships provided by researchers for Iran.