Coprecipitation method is adopted to prepare LiNi0.8Co0.1Mn0.1O2, to discuss the factors of affecting electrochemical properties and structure at lithium ion battery cathode material LiNi0.8Co0.1Mn0.1O2. In order to improve the electrochemical properties of materials, LiNi0.8Co0.1Mn0.1O2 materials were modified by doping the cation of Li or Mg or Al. Through the charge-discharge tests in the range of 2.5~4.3V, the result show that doped Mg samples with a discharge capacity and high efficiency as well as the lowest capacity loss, the initial discharge capacity is 205.9mA.h/g, after 20 cycles the discharge capacity reached 142.4mA.h/g.