In the present work, olivine LiMnPO4 based cathode material is synthesized from a nonstoichiometric mixture of starting materials (the chemical composition can be denoted as LiMn0.8Fe0.19 + 2x Mg0.01P1 + x O4, x = 0.033) and characterized by X-ray diffraction (XRD), magnetic measurement, scanning electron microscopy (SEM) and electrochemical test. The results show that electronically conductive iron phosphides are created on the surface of LiMn0.8Fe0.19Mg0.01PO4 via the controlled nonstoichiometry and can effectively increase electronic conductivity and rate capability of the obtained material.