The precursor of nanocrystalline LiMnPO4 was obtained by solid-state reaction at low heat using Li2SO4 center dot H2O, MnSO4 center dot H2O, and Na3PO4 center dot 12H(2)O as raw materials, maintaining the mixture at 333 K for 4 h, and then washing the mixture with deionized water to remove soluble inorganic salts, and at last drying at 373 K. The nanocrystalline LiMnPO4 was obtained by calcining the precursor. The precursor and its calcined products were characterized using TG/DTA, FT-IR, and XRD. The data showed that the precursor dried at 373 K for 3 h was a compound with amorphous structure. However, when the precursor was calcined at 973 K for 2 h, highly crystallization LiMnPO4 with orthorhombic structure [space group Pmnb (62)] was obtained with a crystallite size of 38 nm. The mechanism and kinetics of the crystallization process of LiMnPO4 were studied using XRD technique, the results showed that activation energy of the crystallization process of LiMnPO4 was 103.30 kJ/mol, and the mechanism of crystallization process of LiMnPO4 is the random nucleation and growth of nuclei reaction.