Abstract: Being able to describe the entity and the entity relationship is a principal feature of databases.It is a basis for the logical design of databases.This paper discusses in detail the description of the entity relationship of 1 1,1 n ,and n m with the high order attributes in O O model,and makes a comparison with the description in relational model. Therefore,O O model has a consistent and efficient method of describing the entity relationship,and it is better than that in relational model.