The differences in spatial patterns of population shrinkage in rural areas within counties and their influencing factors were analyzed to provide empirical evidence and scientific guidance for analyzing the relationship between population and land in rural areas within counties and promoting efficient and intensive use of resources. The precise geographic data including residential patches of rural settlements and LandScan - a high-resolution population distribution dataset- were used to innovatively construct a population shrinkage index. This index was used systematically to detect the dynamic changes in population density of rural areas in China at the patch scale from 2000 to 2020. The spatial patterns of population shrinkage in rural areas across 2 847 counties in China was comprehensively analyzed. The results showed that patches of population shrinkage were prominently concentrated in the Huaihe River Basin， with mild shrinkage mainly observed in rural areas in the western region and severe shrinkage in rural areas along the eastern coast. The population shrinkage in rural areas within counties had significant regional differences， forming a spatial pattern of “two belts and multiple agglomerations”. Counties （cities） with different administrative divisions exhibited differentiated characteristics of population shrinkage. Urbanization （UR）， education service （EDU）， and agricultural mechanization （ARG） were the three pivotal factors affecting the internal population shrinkage in rural areas within counties in China. The interplay between educational service and rural income had the strongest explanatory power.It will provide a robust empirical foundation and scientific direction for dissecting the population -land nexus within counties， refining the plans for rural settlement， and advocating for the efficient， intensive utilization of resources.