α-Fe2O3 hexagonal micro-platelets were prepared via a simple hydrothermal process in the presence of an organic solvent PEG400. The synthetic method was based on the hydrothermal oxidative decomposition and the recrystallization of Fe(OH)3 precursor in a basic solution of NaOH. The crystalline structures and morphologies of the as-obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of the alkali environment during the hydrothermal reaction on product morphology were investigated. According to the results, α-Fe2O3 hexagonal micro-platelets could be directly prepared in a basic solution of NaOH (2.5 mol/L) when using PEG400 in the reaction system. The product morphology changes from rodlike to platelike shape when the alkali concentration increases from 1 mol/L to 2.5 mol/L. Therefore, the use of PEG400 and the hydrothermal growth alkali concentration play an important role in the formation of such platelike microstructure of α-Fe2O3. When the α-Fe2O3 hexagonal micro-platelets are used in Li-ion battery, it exhibits an initial reversible capacity of 674.9 mAh·g-1