In China’s rapid urbanization and industrialization, cities are playing important roles in helping the country reach its climate change mitigation goal of peaking CO2 emissions around 2030, and improving environmental quality. During the 12th Five-Year Plan (12th FYP) period (2011–2015), Chinese cities set ambitious goals and implemented diverse policies aimed at transitioning to a greener economy. The Chinese central government also set targets on a number of indicators, such economic energy intensity and carbon intensity (e.g., CO2 per unit GDP), and air quality (e.g., PM2.5 concentration). These targets are helpful for tracking implementation of individual policies or progress at a sectoral level. However, a more comprehensive and integrated approach is needed to assess progress and capture the multi-dimensional aspects of Chinese cities’ transition to a greener economy, an approach that offers comparison with international best practices, as well as working with data availability in China’s statistical system. This paper presents the development of a China Green LowCarbon City Index2 (CGLCCI, or City Index) and its application to 115 Chinese cities – the largest assessment of Chinese cities to date. The GCLCCI includes 23 key indicators across seven categories: economy, energy, industry, buildings, transportation, environment and land use, and climate policy and outreach. This paper applied the CGLCCI to benchmark the green and low-carbon development status of 115 Chinese cities in the year 2015. Data for the analysis came from government and publicly available data sources. The CGLCCI methodology provides a standardized method to benchmark each indicator, calculate overall city scores, and rank the cities.3 The results showed that the low-carbon transition in Chinese cities is still in its early stages. Compared to the best practices benchmarks, the 2015 City Index scores ranged from a low of 28 to a high score of 70 in 2015 (maximum score is 100). This paper also presents three top-performing cities in different stages of development and discusses how their scores across the index categories. Creating a green low-carbon index that relies on publicly available data in China, and regularly evaluating city performance, can encourage Chinese cities to learn best practices from each other, and to strengthen their goals and implementation efforts toward a green low-carbon transition.