Spherical LiNi0.8Co0.2O2 powders with particle size of 8~10μm were prepared based on controlled crystallization, and coated with Al2O3 by Al(OH)3 sol, that was prepared from Al(NO3)3 and NaOH, at first time. SEM, XRD and surface element analysis showed that the nano-sized Al2O3 was coated uniformly on the surface of LiNi0.8Co0.2O2 powder. At 25 °C, the initial discharge capacity decreased from 160 to 149 mAh g-1 after coating of Al2O3. The initial discharge capacity decreased from 168 to 163 mAh g-1 after coating of Al2O at 55 °C. After coating of Al2O3, the capacity retentions increased from 83.8% to 92.6% at the 50th cycle at 25°C, and from 36.3% to 90.8% at the 10th cycle at 55°C. This paves effective way to improve the performance of LiNi0.8Co0.2O2 material for rechargeable lithium ion batteries.