With the development of information and communication technology, such as mobile internet, cloud computing, and big data, smart city has gradually become the important development tendency of urban construction. During the period of the 13 ^th five-year plan, cities have formulated their smart city construction (or development) plans and regarded these plans as key part of their medium- and long-term urban development strategies. Because smart city involves various context and massive indexes, the assessment of smart cities is undergoing continuous development and improvement. Thus, so far, an unified assessment standard is still lacking. Based on this, we compare the domestic and international index systems to assess smart city development. With the objectives including improving cities' capability of sustainable development, implementing efficient and fair management, and ensuring urban residents' wellbeing, this paper proposes an assessment index system with multiple layers and five sub-systems including smart economy, smart transport, smart healthcare, smart education, and smart management. This paper employs text, webpage, and statistic data and conducts a comprehensive, uniform, and multi-layer assessment to evaluate smart city development status for Chinese cities. finally, we offer constructive suggestion on smart city development from the perspective of sub-system coordination. Main findings are shown here. First, except 8 cities, namely Beijing, Shanghai, Guangzhou, Wuhan, Chengdu, Hangzhou, Tianjin, and Nanjing, most cities are at a relatively low level of smart city development. Second, based on the spatial pattern, cities in the coastland are at a relatively higher level of smart city development than those in the inland. Municipalities and provincial capitals are at an obviously higher smart development level than the other cities. Third, from the coordination perspective, five sub-systems are not coordinated well with more than 70% cities showing moderate- to low-level coordination. Overall, the average development level of smart education and smart healthcare are the lowest among all sub-systems. More than 80% of cities have disadvantages in the two sub-systems. Based on these findings, this paper provides some policy implications for the future development of cities. The government should pay more attention to the coordination of sub-systems, such as smart education and smart healthcare. For smart transport, most cities have already had a high level of development, and the efficiency and fairness of transport development will be more important in the future. Innovation and global development have become the key factors restricting the development of smart economy and should be considered in future policy-making. In addition, government and the relevant departments should strengthen the top-level design, module construction, and index statistics of the smart management.