Mahallat geothermal field having several hot springs is located in Markazi province, at the center of Iranian Plateau. Various studies have been conducted in this field to estimate the depth and location of the thermal resources. The main purpose of this study is to determine the bottom and top depth of magnetic sources of Mahallat geothermal field located in Markazi province. An advanced technique used in spectral analysis called “Forward modeling of the spectral peak “ is used to estimate the bottom and top depth of magnetic layers. This method is used for collecting magnetic field data in Mahallat area, in Marakzei province. The results indicated that the range of variations in the bottom- depth of magnetic springs varies from 1.1 to 2.3 km, which are significantly consistent with the location of hot springs.