[目的/意义]专业分馆在高校图书馆学科服务中一直处于可有可无的边缘地位，互联网+时代，粗放型的学科服务日趋精细化，这使得专业分馆在高校图书馆学科服务中的定位发生变化；重新界定这一定位，有助于为高校图书馆学科服务带来新的增长点，注入生机和活力。[方法/过程]以清华大学图书馆专业分馆的学科服务作为实证，引入定位原理，探讨专业分馆在高校图书馆学科服务中的定位和实现。[结果/结论]设有专业分馆的高校图书馆应该将专业分馆作为学科服务的一线和前沿，以专业分馆为核心，与分馆所属专业的教学、科研工作开展密切合作，深入分析、挖掘教师和学生的信息需求，以知识服务和个性化服务为基本点，构架图书馆与院系等其他相关部门多位一体的泛学科服务机制。

[Purpose/significance] The branch library has always been in the marginal position in the subject service of university libraries. In the Internet+ era, extensive subject service is becoming more sophisticated, which makes the position of a branch library changed in the subject service of university libraries. Redefining the position of a branch library will help to bring new growth points and inject vitality into the subject services of university libraries.[Method/process] Taking the subject service of branch libraries of Tsinghua University as an example, this paper introduces the principle of Position, and probes into the position and realization of a branch library in subject services of University libraries.[Result/conclusion] It is expounded that branch libraries should be regarded as the front line and frontier of the subject service.With the branch library as the core, libraries should cooperate closely with the teaching and scientific research work, and analyze and excavate the teachers and students'information requirements deeply. Based on the knowledge service and personality service, we constructs the multi-disciplinary and ubiquitous subject service mechanism of library and other related departments.