The embedded subject service requires librarians to walk out of the library, observe users' needs through embedding users' researching, teaching and learning process. They should provide users with intelligent knowledge. As a service concept, embedded subject service has been widely applied in American university libraries. The advanced experience of subject service practice in America has important significance for the scientific development of the embedded subject service in Chinese university libraries. This paper investigates the embedded subject service mode and characteristics both in America and China. It makes a comparative analysis of the differences between American and Chinese university libraries in the aspect of the service consciousness, the depth and breadth of embedded service and library marketing efforts. In the last, it makes suggestions on the development of the embedded subject service in China.