LiMnPO4 nanoplates with a thickness of ca. 13nm have been synthesised by a facile solvothermal approach in mixed water-DEG (diethylene glycol) solvents with the mediation of CTAB (cetyltrimethyl ammonium bromide). The coordinative effect of CTAB and DEG promotes the crystal orientation growth of LiMnPO4 along ac plane. The structure and morphology of the product were characterized by XRD, SEM, TEM, BET, FT-IR and Raman spectra. A possible formation mechanism of LiMnPO4 nanoplates assembled in layer-by-layer style is put forward on the basis of the above characterization results. A continuous and uniform carbon layer is coated on the surface of the LiMnPO4 nanoplates after heat treatment with sucrose. The obtained LiMnPO4/C composite exhibits high discharge capacities of 148.6mAhg−1 at 0.1C, 127.6mAhg−1at 1C and 93.8mAhg−1 at 5C and it possesses excellent cycling performance with capacity retention ratios of 96.9% and 92.7% after 100 cycles and 500 cycles at 0.1C and 1C, respectively.