On the basis of combing the relevant research and practice development, this paper puts forward smart librarians, intelligent technology, blended concept and smart content as the key elements of public library's smart service. Then, the paper finds that development path of smart service mainly present some indications，such as from intelligence to smart, from two-way connection to everything connection, from a boundary to crossover. Finally，the paper discusses the main smart service modes and typical cases in the practical field of public libraries from four aspects: resource construction, technological breakthrough, reader demand and space reconstruction.