Li-rich layered xLi2MnO3-(1-x) LiMO2(M=Ni,Co,Mn...) solid solution materials possess high energy density, high capacity, and long cycle life. Meanwhile, the electrochemical charge/discharge mechanism is quite different. In this paper, Li-rich cathode material xLi2MnO3-(1-x) LiMO2(M=Ni,Co,Mn...) is introduced though its structure, charge/discharge mechanism, synthetic methods and electrochemical performance. What is more, the characteristics and development trend of this series of cathode material are summarized.