Abstract: This study investigated the contents of eight heavy metals and related oxides in rocks with different lithologies and the soils formed in the Puhe river basin of Pingquan City. Based on the above investigation, this study analyzed the influencing factors and sources of soil heavy metals in the typical small watershed of the shallow mountainous area, aiming to provide theoretical support for water conservation and ecological restoration in the Beijing-Tianjin-Hebei region. Based on the contents and spatial distributions of soil heavy metals and combined with regional geological setting, this study delved into the influencing factors and sources of heavy metal elements in topsoil, deep soil, and soil parent materials using multiple statistical methods. The results show that heavy metals in topsoil and deep soil exhibited relatively similar contents and coupled spatial distributions. In terms of vertical distributions, the correlation coefficients of heavy metals were negative between topsoil and soil parent materials but positive between deep soil and soil parent materials. As indicated by the results, in the topsoil, elements Cr, Ni, Cu, Zn, and Pb are primarily derived from soil parent materials, while elements Cd, Hg, and As are subjected to the influence of mining. In contrast, the eight heavy metals in the deep soil predominantly stem from soil parent materials, with anthropogenic factors contributing to Cd and As.