Abstract: 【Purpose/significance】Realizing optimization of health information service supply is an important concern for public librar⁃ ies, as important public service facilities, to fully implement the "Healthy China" Strategy.【Method/process】The text starts from the integration of the service subject and the precision of the service content, Construct a basic theoretical framework. On this basis, we carry out multi-case studies based on representative public libraries at home and abroad. This paper puts forward four types of public library health information service: initial type, generalization type, specialty type and ideal type, and based on the main emphasis of op⁃ timization, puts forward three supply optimization paths, namely, the breadth path of "initial type-generalization type", the depth path of "initial type-specialty type" and the breadth-depth path of "initial type-ideal type".【Result/conclusion】It is concluded that the key to the optimization of health information service supply lies in the integration of service subjects, the refinement of service con⁃ tents and the transfer of service costs. It is necessary for public libraries to make active efforts from both breadth and depth, while tak⁃ ing into account cost control, to fully optimize the supply of health information services.【Innovation/limitation】The multi-case analy⁃ sis method provides a new theoretical support and empirical basis for optimizing the supply of health information services in public li⁃ braries. However, there are still some limitations such as lack of quantitative data comparison and rough cost analysis, which need to be further optimized.