A facile precursor-separated hydrothermal synthesis (PSHS) method was developed to synthesize LiFePO4 nano-crystallines at low temperature where the iron sulfate solution precursor was packed in polymer film to divide it from Phosphoric acid and Lithium hydroxide before reaction. X-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were adopted to characterize the morphology and crystal structure of the products. The electrochemical properties and conductivity of the products were also investigated. This method avoided the probably generated Fe3+ at the precursors mixing process. The particle size was reduced to nanoscale without any additives. The as-prepared product showed excellent electrochemical properties especially rate capability. The reaction mechanism of this method was also studied.