In this work we have studied the effects of substitution of lanthanum by Li at the A site on the structural, electrical and dielectric properties of the brownmillerite compounds La1-xLixSrMn2O5+δ(x = 0.05, 0.10 and 0.15). The samples prepared by the sol-gel reaction method. Structural investigation by RX diffraction shows that all compounds crystallize in the cubic structure with space group Pm-3 m at room temperature. The morphology and grain size of the compounds were observed using a scanning electron microscope (SEM). Impedance spectroscopy is used to study the AC electrical properties of these materials in the temperature range 100–200 K and in the frequency range 100 Hz to 1 MHz. To study the dielectric behavior of materials and various physical phenomena. Complex impedance plane plots show the grain contribution for the samples. The Nyquist plot Z' as a function of Z" at different temperatures shows semicircular arcs describing an equivalent circuit.Variation of the modulus and electrical conductivity of the compound shows conduction phenomena and a no-debye type relaxation process. The electrical conductivity was determined using Jonscher's law and the activation energies were determined from the conductivity and the imaginary part of the impedance.