Assessing urban green and low-carbon development quality to promote urban green and low-carbon transformation is essential for reaching the ambitious goals outlined in the "dual carbon" strategy in China. The assessment also plays a crucial role in supporting the overall green transformation of economic and social development. To build the assessment framework,the study adopts a comprehensive approach,integrating efforts focused on carbon reduction,pollution control,green space expansion,and sustainable growth,starting from the understanding that cities operate as complex ecological systems. In exploring the essence of urban green and low-carbon development quality,this study employs the human-environment health circle model to dissect the core elements within various scales of urban spaces. Then,by aligning these elements with the Sustainable Development Goals (SDGs),which were proposed by the United Nations,this study constructs a theoretical framework aimed at evaluating urban green and low-carbon development quality,emphasizing the interaction between multiple spatial scales and diverse goals. Next,a localized evaluation index system is developed. It considers the rationality and feasibility of the selected indicators. This study conducts an empirical analysis using Hangzhou as a case study to apply this index system effectively. Several important findings are revealed. First,the fundamental connotation of urban green and low-carbon development quality is identified as the comprehensive level of achieving synergistic goals such as pollution reduction,carbon reduction,economic growth,and improvement in citizens' livelihoods. Second,the evaluation index system comprises 49 key indicators,which are categorized into three main types: mandatory,orientative,and advocated indicators. These indicators span four spatial dimensions: building,basic unit,infrastructure,and the urban environment. This multi-dimensional perspective ensures a thorough evaluation of urban green and low-carbon development quality. Third,the assessment results for Hangzhou,which span four distinct phases from 2008 to 2023,align well with the actual circumstances observed in the city. This alignment not only validates the scientific integrity of the proposed index system but also demonstrates its practical applicability. Finally,the promotion of high-quality green and low-carbon urban development requires a holistic view that considers strategies and synergies across the four identified dimensions of building,basic unit,infrastructure,and urban environment. Recognizing the development measures of these dimensions allows for more effective policy formulation and urban planning. In summary,this study not only expands the theoretical framework for assessing urban green and low-carbon development quality but also provides practical reference for promoting green,low-carbon and high-quality development in Chinese cities.