A simple and effective method, ethylene glycol-assisted co-precipitation method, has been employed to synthesize LiNi0.5Mn1.5O4 spinel. As a chelating agent, ethylene glycol can realize the homogenous distributions of metal ions at the atomic scale and prevent the growth of LiNi0.5Mn1.5O4 particles. XRD reveals that the prepared material is a pure-phase cubic spinel structure (Fd3m) without any impurities. SEM images show that it has an agglomerate structure with the primary particle size of less than 100nm. Electrochemical tests demonstrate that the as-prepared LiNi0.5Mn1.5O4 possesses high capacity and excellent rate capability. At 0.1C rate, it shows a discharge capacity of 137mAhg−1 which is about 93.4% of the theoretical capacity (146.7mAhg−1). At the high rate of 5C, it can still deliver a discharge capacity of 117mAhg−1 with excellent capacity retention rate of more than 95% after 50 cycles. These results show that the as-prepared LiNi0.5Mn1.5O4 is a promising cathode material for high power Li-ion batteries.