[ Background ] Riparian soil and vegetation along rivers are important for biodiversity maintenance and biogeochemistry circulation of river ecosystems, and are the basis of many ecosystem services. Influenced by human activities and natural factors, soil structure and vegetation in the riparian buffer zone of the middle and lower reaches of the Yellow River are subjected to degradation to a certain extent. [Methods] Selecting the Zhengzhou-Kaifeng section of the middle and lower reaches of the Yellow River as the studied area, as well as using methods of field investigation, experimental analysis,and canonical correspondence analysis (CCA), the present study was conducted to investigate the fractal dimension characteristics of riparian plantation soil particle size at the surface layer of 0 - 20 cm under different vegetation types and buffer distances. [Results] The results indicated that the soil particle size distribution (PSD) was heterogeneous with higher contents of silt and clay (more than 75.5%) and less content of sand. However, soil texture was uniform in spatial, since no significant difference was observed between Salix matsudana plantation and Populus tomentasa plantation as well as among the four riparian buffer zones ( < 1.5 km, sample number (n) = 13; 1.5 -3 km, n = 11; 3 -4.5 km, n = 11; > 4.5 km, n = 12). The fractal dimension ( D) value was approximately equal to 2.75, suggesting a fine soil structure with favorable performance in the retention of water and fertility in the studied area. Result from Pearson correlation analysis indicated that D value and clay content were significantly and positively correlated with soil total carbon (TC), total organic carbon (TOC), and total nitrogen (TN) at the 0.01 level, on the contrary, sand content was significantly and negatively correlated with TC, TOC, and TN at the 0.01 level, while silt content was only significantly and positively correlated with TN at the 0.05 level. Result from CCA indicated that the community characteristics such as the herb height, tree diameter of breast height, tree height, and tree cover were related positively and closely with D value, silt content, and clay content, while were negatively correlated with sand content, suggesting that the larger tree coverage and biomass can lead to the better soil structure. Moreover, inconsistent with other research results, the soil particle size distribution and fractal dimension characteristics were less affected by elevation because of the small gradient variation in the studied area. [Conclusions] The riparian buffer zone of the middle and lower reaches of the Yellow River, which is affected by both human activities and natural factors, is subjected to serious issues of soils such as loose structure, decreased organic matter content, and significant desertification, thus results from this study can provide basis for ecological restoration, bank erosion control, and land management of the degraded riparian zone.