Abstract: Rural poverty was a persistent problem in human society, and a common challenge faced by the whole world, where China is no exception. Many untiring efforts have been made to completely eliminate absolute poverty in China to achieve the goal of poverty reduction 10 years ahead of schedule in the United Nations 2030 Agenda for Sustainable Development. After that, the anti-poverty focus has changed into rural relative poverty since 2020. It is necessary to continuously narrow the development gap between urban and rural areas, thereby promoting the rationed sharing of development achievements. It is highly urgent to quantitatively determine the relationship between rural relative poverty and regional carrying capacity, thereby providing a scientific basis for the simultaneous formulation of intervention measures. Taking the Yangtze River Economic Belt (YREB) as the case area, this study aims to explore the spatial pattern of rural relative poverty and the constraint mechanism of regional carrying capacity. Multi-source databases were established using 1 070 county-level administrative units, including the rural social economy, resources, environment, road traffic, and major function zones. The areas of rural relative poverty were defined to identify the change types. The spatio-temporal evolution of rural relative poverty areas since 2010 was then determined from the multi-scale of the river basin, county, and major function zones. At the same time, an index system of regional carrying capacity was established to quantitatively evaluate the level of relative poverty restricted by regional carrying capacity in rural areas of YREB. Six elements were composed of land resources, water resources, environment, ecology, disaster, and transportation. Furthermore, the hierarchical clustering and binary logistic regression model were used to clarify the poverty-causing effect and the constraint level of regional carrying capacity. The results showed that: 1) The number and population size of rural relative poverty areas in the YREB decreased from 353 and 133.666 million in 2010 to 237 and 89.922 million in 2018, indicating that the precise poverty alleviation strategy was achieved to effectively reduce poverty. 2) The spatial pattern of rural relative poverty areas was generally stable and partially shrinking. Key ecological function zones were focused mainly on stable distribution in Wumeng Mountain, Wuling Mountain, Luoxiao Mountain, Yunnan-Guangxi-Guizhou rocky desertification areas, and western Yunnan Border Mountain. The counties without rural relative poverty were located mainly in the urban agglomeration areas or the periphery of central cities. 3) Ordinal logistic regression model showed that transportation, ecology and disaster carrying capacity were the important factors leading to rural relative poverty in the YREB. The probability of rural relative poverty increased by 120.85%, 30.59%, and 42.43%, when the constraint level of three factors increased by one grade. The probability of poverty in urbanized areas and main agricultural production zones was only 19.87% and 66.00% of that in ecological function zones. 4) There was an obvious conjugacy relation among the carrying capacities of each factor in the rural relative poverty areas, showing the characteristics of global transportation dominance and comprehensive constraints of local ecology, disasters, and land resources carrying capacity. It was suggested to design a differentiated anti-poverty policy system using the constraint degree of regional carrying capacity and the type of regional function, thereby realizing the two-way promotion of sustainable development ability on the regional scale, particularly on the individual ability of sustainable livelihood with farmers as the main body.