Flower-like LiMnPO4 nanostructures self-assembled with (010) nanosheets were successfully synthesized via a simple hydrothermal method by employing MnSO4 and Li2SO4 as raw materials and EG-H2O mixture as reaction medium solvent. The flower-like LiMnPO4 were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, respectively. The primary LiMnPO4 nanosheets are about 30 nm in thickness and dominated with (010) facets. In order to understand the formation mechanism of the flower-like LiMnPO4 nanostructures, a series of time-dependent experiments were adopted. Based on the experimental results, a possible mechanism was proposed for the formation of LiMnPO4 nanosheets and the assembly of the flower-like nanostructures. Additionally, the electrochemical performances of the flower-like LiMnPO4 nanostructures as cathode materials in Li-ion battery were also investigated by charge-discharge measurements.