Abstract: The Chongzuo area, located in southwestern Guangxi, encompasses Jiangzhou District, Daxin County, and Longzhou County, with the majority featuring karst topography. This study focused on 242 samples of rice grains and their corresponding rhizosphere soils from contiguous farmland in the region. These samples were analyzed to measure the contents of 26 elements in the soils, including arsenic (As), cadmium (Cd), and chromium (Cr), as well as the contents of As, Cd, mercury (Hg), and lead (Pb) in rice grains, using inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), and atomic fluorescence spectrometry (AFS). By analyzing the characteristics of heavy metals in soils and rice grains, the influencing factors and fitting models of heavy metals from soils to rice grains were investigated. The results indicate that the content of oxides in soil was generally lower than the national average, while the content of heavy metals was relatively high, especially Cd and Hg. As and Cd in soils exhibited relatively high pollution risks. The contents of As, Cd, Hg, and Pb in rice grains from non-karst areas were generally higher than those from karst areas. The contents of As, Cd, Hg, and Pb in rice grains generally complied with food safety standards. As and Pb in rice grains showed significant correlations (dominated by negative correlations) with metal elements, non-metal elements, and oxides in rhizosphere soils, while Cd and Hg exhibited significant correlations with oxides in rhizosphere soils. Various fitting models of As in rice grains generally presented a coefficient of determination (R²) above 0.5, indicating better model performance than those for Cd, Hg, and Pb. After distinguishing between karst and non-karst areas, the R² values of the fitting models were further improved. Among the factors influencing the contents of As, Cd, Hg, and Pb in rice grains, parent material played a more significant role than rice variety. This study preliminarily clarifies the key driving factors of heavy metal transfer in the soil-rice system in the karst area of Chongzuo, providing a theoretical and practical basis for the safe production of agricultural products, classification-based management of contaminated farmland, and policy formulation in similar karst areas of Southwest China.