As a user centered service, Subject Information Service in NSL is based on subject librarian’s service, with the support of National Science Technology Library (NSTL) and Chinese National Science Digital Library (CSDL). Fully considering the change of information environments and needs of CAS users, the service support independent innovation research with subject, knowledge and personalized services under the principle of “be available at the first line and embed into the process”. All subject librarians put their services and innovations into the institutes, accordingly, they must be responsible for the institute and accept evaluation from institutes. Diversiform, extensive, convenient and prompt information services are provided for the institutes, research groups, labs, individuals or users’ virtual spaces.