Throughfall in shrub canopies of arid regions is a pivotal link in maintaining the ecosystem water cycle and supporting the normal growth of vegetation. Its spatial heterogeneity is not dominated by a single factor but synergistically regulated by multiple elements such as canopy structure, rainfall characteristics and microenvironment. Clarifying the distribution pattern and driving mechanism of this characteristic is of great significance for understanding the eco-hydrological processes in arid regions. In this study, Caragana korshinskii and Salix psammophila, two typical xerophytic shrubs on the Loess Plateau, were selected as the research objects. Fixed-position field monitoring was carried out during the rainy seasons of 2016 and 2017 for two consecutive years to systematically explore the spatial distribution pattern and intrinsic driving mechanism of throughfall in the two shrub species. The results showed that the throughfall of both shrubs exhibited significant spatial heterogeneity, with their coefficients of variation reaching 20.95% and 20.17%, respectively. And there were statistically significant differences in throughfall distribution at different positions under the canopies (P＜0.05). This spatial heterogeneity is comprehensively regulated by the shrub canopy morphological structure and rainfall characteristics such as precipitation amount and rainfall intensity, and the synergistic effect formed by the two jointly shapes the spatial distribution pattern of throughfall. Specifically, the canopy morphological structure changes the spatial distribution characteristics of throughfall under the canopy by directly regulating the processes of rainfall interception and redistribution. Quantitative analysis results confirmed that canopy thickness and branch length are the key morphological factors affecting the spatial heterogeneity of throughfall (P<0.05). Rainfall characteristics indirectly regulate the spatial heterogeneity pattern by determining the supply quantity and input intensity of throughfall under the canopy, which is specifically manifested in that the coefficient of variation of throughfall under the canopy decreases in a power function relationship with the increase of precipitation amount, rainfall intensity and rainfall duration. In addition, under the combined action of canopy morphological structure and rainfall characteristics, the throughfall of both shrub species showed a certain aggregation effect with obvious interspecific differences, and the occurrence rates of aggregation effect of C. korshinskii and S. psammophila were 8.16% and 2.41% respectively. This study not only provides key data for further understanding the hydrological processes and vegetation water utilization mechanisms in the shrubland ecosystems of arid regions, but also offers important theoretical insights and practical guidance for optimizing vegetation configuration and managing regional water resources efficiently in the restoration of degraded ecosystems in arid regions.