[Purpose/significance] Subject librarian is the main force of library development and subject construction. At present, there are some problems in the professional construction of subject librarian in China, such as low profes? sional level, lagging professional development, and lack of management system. How to effectively promote the profes? sional development of subject librarian has triggered academic thinking. [Method/process] The article lays a theoreti? cal foundation by analyzing the career evolution of subject librarians; Then combine the recruitment data of subject li? brarians in some famous universities at home and abroad to explore the construction of the subject librarian system in domestic double-top universities, and analyze the practical needs for the development of professional ability of subject librarians; Finally, the paper puts forward the optimization path of subject librarian career construction that meets the needs and promotes development. [Result/conclusion] Based on the professional needs and development of subject li? brarians, libraries should formulate scientific professional development system and professional ability promotion strat? egies for subject librarians from four aspects: optimizing the ability system, strengthening knowledge management, im? proving talent training, and paying attention to attitude guidance, so as to cultivate high-quality subject librarian talent team, and help the national scientific research development and economic prosperity.