Nanoparticles of spinel ferrite of the chemical composition Li_0.5-0.5x Mnx Fe_2.5-0.5xO₄ ; x= 0, 0.25, 0.5, 0.75 and 1 were prepared by sol-gel autocombustion technique. The effect of Mn+2 –ions on crystalline phase formation ,morphology, cation distribution and magnetic properties of Liferrite were investigated by X-ray diffraction (XRD), Transimition electron microscopy (TEM), IR spectroscopy and Vibrating sample magnetometer (VSM) .Also the effect of heat treatment on microstructure of Li0.5Fe2.5O4(x=0) has been correlated to magnetic properties whereas the well crystallinity and single phase are confirmed by X-ray and TEM for annealing temperature (Ta=400,600,800) .It`s observed that the addition of Mn+2 – ions promotes the saturation magnetization(Ms) until (x=0.5), then appreciable decrease occurs due to Yafet-Kittel arrangement. The decrease in Curie temperature (Tc) was remarkable. So, the substitution of Mn+2 – ions plays an important role in changing the physical and magnetic properties of lithium-manganese ferrites.