To investigate the effects of under-forest cultivation on the accumulation of mineral elements in Polygonatum kingianum, this study systematically compared soil physicochemical properties, the total and available contents of nine mineral elements in soil, and differences in element contents within the plants between under-forest planting and traditional planting modes in Qujing City, Yunnan Province. Pearson correlation analysis and redundancy analysis (RDA) were applied to reveal the environmental driving mechanisms. The results showed that soil pH, organic matter, total nitrogen, alkali-hydrolyzable nitrogen, and electrical conductivity (EC) under the under-forest mode were significantly lower than those under the traditional mode, whereas the carbon-to-nitrogen (C/N) ratio was significantly increased. In the under-forest soil, the total contents of Fe, Mn, Cu, Zn, Co, As, Pb, and Ni were significantly higher than those in the traditional mode, with an increase of 24.1%-252.4%; however, their available contents were significantly decreased (except for Co and As), with a reduction of 64.0%-77.9%. The mineral element contents within the plants exhibited varying differences under the two cultivation modes. Specifically, the contents of Fe, Cu, Co, and Pb showed significant differences (P < 0.05), with Pb exhibiting a highly significant difference (P < 0.01). No significant differences were observed in the contents of Mn, Zn, Cd, As, and Ni. Under the under-forest mode, the Cu content increased by 12.5% compared with the traditional mode, whereas the contents of Fe, Co, and Pb decreased by 64.2%, 87.4%, and 79.5%, respectively. PCA and RDA demonstrated that the elemental composition characteristics of P. kingianum under the two cultivation modes were distinctly separated. Traditional cultivation was primarily driven by soil fertility factors, whereas under-forest cultivation clustered toward regions characterized by low pH and high total soil heavy metal contents. Soil Pb and Zn exerted significant antagonistic effects on the accumulation of Fe, Co, and Ni within P. kingianum. In conclusion, under-forest cultivation significantly altered the physicochemical properties and chemical speciation of mineral elements in the rhizosphere soil of P. kingianum, thereby reshaping its mineral element absorption and accumulation characteristics.