LiNi0. 5 Mn1. 5 O4 was prepared under various conditions by one-step solid-state reaction in air and its properties were investigated by X-ray diffractormetry (XRD), scanning electron microscopy (SEM) and electrochemical measurement. XRD patterns show that LiNi0. 5 Mn1. 5 O4 synthesized under various conditions has cubic spinel structure. SEM images exhibit that the particle size increases with increasing calcination temperature and time. Electro chemical test shows that the LiNi0. 5 Mn1.5 O4 calcined at 700 ℃ for 24 h delivers up to 143 mA · h/g, and the capacity retains 132 mA · h/g after 30 cycles.