The impedance analysis of magnesium substituted lanthanum in LaFeO3 with a general formula La1-xMgxFeO3 (x = 0.0, 0.1, 0.2, and 0.3) were investigated. The (La,Mg)FeO3 materials were successfully prepared by sol-gel method following sintering process to form bulk material. X-ray diffraction (XRD), X-ray Fluorescence Spectroscopy (XRF) and Impedance spectroscopy (IS) method were used to identify the lattice structure parameters, composition and electrical properties of (La,Mg)FeO3. The Rietveld analysis of the XRD indicated that these perovskite materials are well fitted with an orthorhombic structure and space group Pnma. Mg-substitution caused the crystallite size and dielectric constant (ϵ') to decrease from 7.7x104 to 0.9x104. XRF analysis gives the qualitative composition of (La,Mg)FeO3 materials and also confirmed the presence of La, Mg, and Fe respectively. Nyquist plot of complex impedance becomes higher with Mg substituted due to hole carrier. The presence of polarization from space charge were explained from real part impedance analysis at low frequency. The independent behaviour of dielectric constant was observed at high frequency. Meanwhile tanδshows higher value as increasing of Mg concentration due to the low density of (La,Mg)FeO3 materials.