Abstract: Climatic aridity-humidity variations on orbital timescales are crucial for understanding the Earth's climate system response mechanisms. Investigating the relationship between orbital-scale eccentricity cycles and aridity-humidity changes helps clarify the mechanisms by which Earth’s climate system responds to astronomical forcing. This paper systematically summarizes how eccentricity drives regional moisture variations by modulating precession-induced seasonal solar radiation distribution, supported by case studies from diverse regions. When Earth's orbit approaches a perfect circle (i.e., eccentricity is close to zero), the influence of precession on the distribution of solar radiation is minimal, thereby weakening its capacity to modulate the climate system. In contrast, during periods of higher eccentricity, when the orbit is more elliptical, precession significantly enhances the seasonal contrasts and alters the spatial and temporal distribution of climate zones. Moreover, precession determines the timing and geographic position of perihelion. For example, when Northern Hemisphere summer occurs near perihelion, that region receives stronger summer insolation while winter insolation decreases, intensifying seasonal temperature differences and exerting profound effects on precipitation and evaporation. By synthesizing geological and climatic records from multiple representative regions across Eurasia, this study analyzes how different areas respond to eccentricity-driven hydroclimate variability. Most existing studies suggest that high eccentricity periods are generally associated with more humid environments. This is mainly attributed to stronger seasonal contrasts under high eccentricity conditions, which enhance monsoonal circulation and increase precipitation in monsoon-dominated regions such as East Asia, South Asia, and Africa. In addition, eccentricity may exert indirect control over regional hydroclimate patterns through its influence on high-latitude ice sheet size and the seasonal distribution of solar radiation. However, due to variations in latitude, dominant climate systems, the type and resolution of geological records, and whether the region is influenced by ice sheets, the effects of eccentricity on regional climate are highly complex and spatially heterogeneous. For instance, in areas dominated by the westerlies or located in mid-latitudes, climate changes may show an anti-phase relationship with eccentricity cycles. In these regions, high eccentricity may enhance processes where evaporation exceeds precipitation, strengthen monsoonal activity while suppressing the Mongolian anticyclone, or alter the position and intensity of the westerlies, leading to hydroclimate responses that are opposite to the general trend of eccentricity variation. And during low eccentricity periods, the modulation of precession amplitude is weak, resulting in a relatively stable climate that may favor vegetation growth and the maintenance of ecosystems. Therefore, when exploring the mechanisms by which eccentricity regulates regional hydroclimate change, it is important to avoid the mechanical application of a single region’s climate response pattern. Instead, one must comprehensively consider the modulation of precession amplitude by eccentricity, as well as key regional factors such as geographic location, paleogeographic setting, geological record type, and the developmental stage of ice sheets, to conduct more targeted and systematic analyses.