The requirements engineering process has been defined as the set of activities that deal with problem domain understanding, requirements elicitation, requirements analysis and specification identification. It could enhance the effectiveness of complicated outsourcing issues of developing smart city innovative services that exists ambiguous and different stakeholders’ requirements and public needs. The purpose of this paper is to propose a design methodology of conceptualizing smart city services based on information and communication technology (ICT) so as to enhance the domain understanding and specialized service concept. It aims to find an approach to understand the context among living problems, public needs and innovative services as the fundamental design requirements. Thus, a use-case driven design framework was proposed. Above 50 global use cases of smart city innovative services are collected and feature analysis were conducted. Then, we conceptualized six smart city services, namely (1) Ubiquitous cultural creative street side integration services, (2) Smart food and restaurant services, (3) Future make-up and fast fashion services, (4) Smart living experiential marketing services, (5) Entertainment-based innovative services, (6) MICE (Meeting, Incentives, Conference and Exhibition) Integrated Services. The design requirements and service specification are analyzed and identified by expert panel approach and questionnaires to consider different stakeholders’ considerations and users’ requirements. Then, an outsourcing guidance for public services of smart city are illustrated.