###### Abstract
At the national level, it is believed that the evolution of urban spatial structure is moving towards agglomeration and polycentricity [29; 30]; at the provincial and city cluster level, there are more relevant studies, which focus on the spatial structure of cities and city clusters in economically developed regions and the factors and influences that play a role in them, as well as comparative studies on different urban spatial structures [9; 10]. The urban spatial structure represents the distribution of human, material, financial, and other factors in the city, which also play an important role in changes in the ecological environment [31]. In 1990, German scholars [PERSON] and [PERSON] proposed the concept of eco-efficiency. The so-called \"eco-efficiency\" refers to the provision of goods and services to meet human needs and improve the quality of life at the same time, so that the ecological impact and resource intensity are gradually reduced to a level consistent with the carrying capacity of the earth. The assessment of urban eco-efficiency is one of the important indicators of sustainable urban development and one of the key tasks to promote the construction of ecological civilization. Currently, the research on eco-efficiency can be summarized in the following aspects: From the research content, it mainly includes the construction of the eco-efficiency index system [32], the evaluation of eco-efficiency [33], and the exploration of eco-efficiency regional differentiation factors [34]. In terms of research scale, it mainly includes the discussion of macro-level eco-efficiency of the country [34], province [35], watershed [36], city cluster [37] and other macro-level eco-efficiency, as well as meso-level eco-efficiency of agriculture [34], industry [38], and tourism [39]. [PERSON] et al., studied the relationship between the spatial structure and water ecological footprint of urban agglomeration by taking the water consumption of urban agglomeration as their research object [40]. In relevant studies on urban health and sustainable development, carbon emissions have been widely used as an indicator of urban green economic development [41; 42]. [PERSON] et al., analyzed the relationship between the urban ecological environment and spatial structure from the perspective of urban pollution [43]. [PERSON] et al., analyzed the spatial-temporal coupling relationship between regional carbon revenue and urban spatial form in the Yangtze River Delta urban agglomeration by using carbon emissions data [44]. [PERSON] et al., studied the carbon emissions of Chinese cities and found that China's carbon emissions intensity has a downward trend; the emissions intensity presents a spatial pattern of \"low in the south and high in the north\", and the differences among different regions tend to expand [45]. [PERSON] analyzed the coupling coordination between ecosystem health and urbanization in the Yellow River Basin from the perspective of resource consumption [46]. In general, research on the coupling of urban spatial structure and ecological environment presents a diversified research trend [47]. Although there have been a number of studies focusing on the evolution of urban spatial structure and eco-efficiency in Shandong Province, there are still research gaps. First, most of the existing studies have focused on a single city or a small area, lacking a comprehensive analysis of the evolution of urban spatial structure across the whole of Shandong Province. Second, for the relationship between the evolution of urban spatial structure and eco-efficiency, existing studies mainly focus on qualitative descriptions and case studies, and they lack systematic quantitative analysis and in-depth understanding. Therefore, this study aims to fill this research gap by exploring in depth the evolution of urban spatial structure and its response to eco-efficiency in Shandong Province through the integrated use of spatial analysis methods, theories, and methods of urban economics and ecological economics.