In this project, we have investigated the effects of grain size on the electrical and magnetic properties of LaMnO 3 powder samples. Then the effect of sintering temperature and LMO doping on the structure, magnetic and magnetotraort properties of La 0.8 Sr 0.2 MnO 3 (LSMO)/xLaMnO 3 (LMO) composite have been investigated. The resistivity of LMO samples increases by the decrease of grain size. All samples show the paramagnetic to ferromagnetic transition. The saturation magnetization decreases by increasing milling time. An increase of the width of the transition and a small reduction of the transition temperature, T c , are observed. All of LSMO/xLMO samples show the paramagnetic to ferromagnetic transition. Results show that the rate of decreasing of transition temperature is much higher for high temperaure sintered samples. The presence of LMO at the surfaces of the grains increases the magnetically disordered states in the surface, suppresses the double exchange mechanism. Therefore the magnetization and transition temperature decreases by the increase of LMO concentration.