In view of the lack of sustainability of public welfare services to a certain extent, the work aims to study the feasibility of nudge theory to intervene in public service design, and summarize the nudge strategies applicable to public service design. Firstly, service design was subdivided from the perspectives of service providers, service cores and service models, the concept of public service design was defined accordingly, and classified according to the different resources of service objects. Secondly, from the perspective of service object behavior, the design of public welfare service was divided into four stages. According to the behavior elements in the analysis stage of Fogg's behavior model, the boosting principle was divided into stages. Finally, different types of public service design cases were analyzed to verify the nudges principles available at each stage, and summarize the staged nudging strategies from service contact points. The theoretical and practical cases can prove the good adaptability of nudge theory and public service design. The nudge theory provides new ideas for the study of public welfare service design, which is conducive to promoting the positive cycle of service process realization.