Abstract: This study compared soil texture, soil bulk density, soil moisture content, soil nutrition content, soil pH at 0–30 cm soil layers among low hill rainforest and rubber plantations of different ages in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, Southwest China, based on the method of combining field observation and laboratory test. It further analyzes the changes in soil productivity during the conversion of representative tropical seasonal rainforests into rubber forests, as well as during the production and management processes of rubber plantations. Results showed that it significantly altered soil characteristics beneath the canopy during the conversion of tropical seasonal rainforests to rubber plantations, and the subsequent planting, development, and management of these rubber plantations. This transformation has significantly enhanced the differences in soil properties and productivity between the same soil layers in low-hill rainforests and rubber plantations. The planting and management practices of rubber plantations have significantly increased the clay content in the 0–30 cm soil layer beneath the canopy, while simultaneously exacerbating soil acidification. Those were relatively high for the clay content, soil organic matter content, and water retention capacity of the 0–30 cm soil in 20-year-old rubber plantation. The soil productivity of which was 58.48%, 73.34%, and 136.80% higher than that of the low hill rainforest, 30-year rubber plantation, and 10-year rubber plantation, respectively. The conversion from tropical seasonal rainforest to rubber plantations altered soil structure and reduced soil productivity. High-investment artificial assistance can optimize the combined physical and chemical properties of rubber plantation soils and improve soil productivity. However, soil productivity might decrease with long-term crop harvesting while simultaneously reducing nutrient and maintenance management inputs.