High-voltage LiNi0.5Mn1.5O4 cathode material has attracted much more attention. In this work, spherical LiNi0.5Mn1.5O4 (LNMO-S) cathode material has been successfully prepared via surfactant-assisted co-precipitation method with sodium dodecyl sulfate (SDS) as a surfactant. Influence of SDS addition on the morphology and electrochemical performance of LiNi0.5Mn1.5O4 cathode materials were investigated. The results showed that LNMO-S cathode material prepared via surfactant-assisted co-precipitation method had ranking electrochemical performance; the initial discharge capacity was 135.5 mAh·g−1, over 100 cycles the discharge capacity with the capacity retentiveness was 96.9% at a rate of 0.2 C, the discharge capacities were 120.2 mAh·g−1, 116.4 mAh·g−1, and 96.7 mAh·g−1 at the rate of 1.0 C, 2.0 C, and 5.0 C, respectively. It had a well rate performance and stability. It is exhibited that surfactant-assisted co-precipitation method with SDS as surfactant is a promising technology to preparate of LiNi0.5Mn1.5O4 cathode materials for lithium-ion battery.