Relationship between refractive index and packing density of coatings prepared by glancing angle deposition is analyzed and three expressions are given firstly. And then optical characteristics of the graded-index coating, which is deposi ted as the linear changing of packing density, are discussed from some aspects a s positive or negative change,integral periods or have hale period,different per iods etc, and more over, the influences of different refractive-index theories on the optical characteristics are compared. Finelly, the preparation method,ap plications and some problem in preparation of the graded coating are discussed s eparately.