Abstract: High-purity and well-crystallized LiFePO4 powders with uniformly distributed fine particles were synthesized in a direct hydrothermal reaction. The microstructure and morphology of the samples were characterized via XRD, SEM and constant current charge-discharge cycle test so as to investigate the influences of hydrothermal temperature/time on the electrochemical properties of as-prepared LiFePO4 powder. The results showed that increasing hydrothermal temperature/time benefits the improvement of crystallinity but coarsens the particles. The best electrochemical properties of the LiFePO4 hydrothermally synthesized are found at 200°C/5 hr with a specific capacity 138.0 mA·h·g^-1 at 0.1C rate during initial discharging. It means that the hydrothermal synthesis is commercially practical. Moreover, adding the ascorbic acid and glucose in the hydrothermal synthesis can avoid efficiently the oxidation of Fe²⁺, thus enhancing the electric conductivity of LiFePO4 powder.