Since the 18th National Congress of the Communist Party of China, the country has significantly strengthened ecological and environmental protection, making major strides in building a “Beautiful China” and advancing toward a comprehensive green transformation of its economy and society. To support broader participation in the green and low-carbon transition and the co-creation of livable cities, the Institute of Public & Environmental Affairs (IPE), with technical guidance from the Chinese Research Academy of Environmental Sciences and support from the Energy Foundation, developed the City Green Synergy Index and launched a public participation platform. In the first evaluation covering 100 cities, Ningbo, Shenzhen, and Beijing ranked in the top three, followed by Guangzhou, Chengdu, Weihai, Fuzhou, Kunming, Yichang, and Xiamen in the top ten. Eastern coastal cities like Ningbo, Guangzhou, and Weihai stood out for overall performance, while Fuzhou and Xiamen led in environmental quality. Megacities such as Beijing and Shenzhen showed strong results in high-quality development. In the southwest, Chengdu and Kunming led on climate action through coal-to-electricity initiatives and non-fossil energy expansion, while Yichang in central China stood out for its ecological restoration efforts.