P. Barr� et al. put forth a hypotheses in 2007 that in soils of the temperate zone plant’s uplift of potassium and silicon from lower soil horizons buffers K and Si depletion from illite-like minerals (illite and illite/smectite) in the upper soil horizon, thus leading to the long existence of high amount of illite-like minerals. To verify whether the hypothesis exists in soils of the tropical region, chronosequence soil samples were selected from 6 profiles (1×10⁴ a, (9.0±2.0)×10⁴ a,(14.6±0.9)×10⁴a, 64×10⁴ a, (133±18)×10⁴ a, （181±8）×10⁴ a) derived from Quaternary basalts formed after volcano eruptions in different time periods in Hainan Island, southern tropical China, for analysis of the variation of clay minerals in these soils, using the classical X-ray diffraction technique. Soil potassium, silicon, and active silicon of the samples were also determined. Results show that illite-like minerals existed only in the soils older than (133±18)×10⁴ a, where the contents of potassium and silicon were found to be higher in the upper soil horizons than in the lower soil horizons, while a contrary tendency was detected with the content of gibbsite, and the content of active silicon generally decreased with the soil age. Consequently, it is held that during the forming process of the soils of the tropical regions, P. Barr� hypotheses might exist in the initial period of soil development, and in the presence of biological complex potassium and complex silicon as well, but it would disappear finally due to the intensive K and Si depletion of the soils in the tropical regions.