LiNi0.75Co0.15Mn0.1O2 was prepared by solid state reaction and its crystal structure was studied by Rietveld Refinement. The result shows that the oxygen octahedron surrounding transition elements in LiNi0.75Co0.15Mn0.1O2 is distorted. The lengths of twelve edges of the octahedron are different. The lengths of twelve edges divided into two groups and their length is 2.7098Å and 2.8780Å respectively. The analysis shows that the change crystal fields due to transition metals and lithium ions results in the different length of octahedron edges in LiNi0.75Co0.15Mn0.1O2.