Based on quantities of clients and venders in Information System(IS) Outsourcing relationship, this article will distinguish four kinds' relationships of Outsourcing, as follows: one-to-one, multi-vendor, co-sourcing, and complex multi-vendor, multi-client relationships. The paper has been not only explained every relationship of Outsourcing in detail, but also analyzed the enabled factors and limited factors during one-to-one relationship developing to the followings. It was very important to guide enterprise to implement IS outsourcing relationship management.