Plant fine roots play a key role in water and nutrient uptake, yet, are not studied as much as leaves. Fine roots traits, particularly the pressure-volume (P-V) curve and anatomical-structural characteristics, are important in determining plant adaptation to changing environment. However, limited information regarding the variation of these traits in response to soil rock fragment content (RFC), especially in drought-prone rocky mountain areas. To address it, a four-year-long field experiment was conducted with four soil RFC levels (0%, 25%, 50%, and 75% ν ν−1) and four dominant xerophytic species. The objectives were: 1) to explore the response of fine root functional traits to RFC gradients, and 2) to identify the driving factors in the variations in fine roots traits. Results found that the fine roots of xerophytes adapted to high soil RFC conditions by enhancing water storage, capacitance, and wilting resistance. This strategic adaptation was highly related with alterations in fine root anatomical-structural traits, e.g., cortex thickness, root diameter, specific root length (SRL), and other P-V traits, including a more negative osmotic potential (Posm) and a lower cell bulk modulus. Importantly, our findings highlight the role of non-capillary porosity in impacting water storage, capacitance, and SRL, as well as the impact of soil available nutrients (e.g. nitrate nitrogen, available phosphorus) in shaping Posm and turgor loss point. This research contributes to a deeper understanding of the survival strategies and mechanisms of xerophytic species in rocky soils, and highlights the coupled relationship of fine root P-V traits and soil properties in determining the species' geographical distribution boundaries.