As one of the most important physicochemical properties of dietary fiber powders, the water-interacting property is closely related to their technological properties and physiological functions in the food system. However, systematic research is unavailable on the relationship between the water-interacting properties and the composition and particle structure of dietary fiber powders. Therefore, the water-interacting properties of dietary fiber powder and these dependence on composition and particle structure by correlation analysis were investigated, based on the determinations of the hydration properties (water holding capacity, swelling capacity), hygroscopicities (initial absorption rate, absorption time, maximum absorption rate), dietary fiber contents (total dietary fiber, soluble dietary fiber and insoluble dietary fiber), and particle structure (particle size, span, specific surface area, pore volume, pore size) of 40 kinds of dietary fiber powders. The results showed that the water holding capacity of dietary fiber powder was positively correlated with its swelling capacity, while the correlation between its hydration property and hygroscopicity was not significant. In contrast, the hydration property was more depended on the fiber composition than the particle structure. The water holding capacity of the dietary fiber powder were consistent with the uniformity of the particle size. However, the hygroscopicity had no significant correlation with neither the composition or particle structure.