After the Smart City initiative was put forward, cities all over the world started the pilot practice of developing Smart Cities. This triggered a series of thoughts: what is a Smart City, how do we determine the scope of work of a Smart City, and how do we formulate a new strategic agenda of the Smart City to make city smarter and more sustainable? The answer lies not only in finding Smart City solutions, but also leads to the research on the definition of Smart City terminology and the determination of corresponding tasks. Stakeholders of Smart City (e.g., policy makers, municipalities, solution providers, industry, and academia) develop technical and management standards for these tasks jointly. This paper reports the standardization planning on Smart City by the international standardization development organizations (SDOs), that is, the standardization framework of Smart City. It also presents one of the important aspects, namely, the progress of standardization activities on urban infrastructure that are being carried out by the International Telecommunication Union (ITU) via its Study Group 20, in supporting the adoption of information and communication technologies (ICTs) in Smart City. These standards include the classification of urban infrastructure, the interoperability between urban infrastructure and smart city platforms, and the requirements of detailed infrastructure from the perspective of ICT and the Internet of things (IoT). This paper also provides the use cases of application of some standards in global cities.