【Objective】The stoichiometry of base cations and silicon (BC:Si) can quantify the impact of soil mineral weathering on soil acidification process, which plays an important role in quantifying soil acidification rate in the current environment. The purpose of this research is to explore the BC:Si difference and its causes in Udic Cambosols derived from three parent materials of Mica schist, Gneiss and Andesite.【Method】First of all, the physical, chemical and mineralogical properties of test soils were measured, and then the release of base cations and silicon of soils derived from three parent materials were obtained by Batch method under leaching of simulated acid rain. In order to avoid the influence of base cations adsorbed by soil colloid on the stoichiometry of mineral weathering process, the soil exchangeable base cations were washed by elution experiments.【Result】The results showed that content and distribution in profile of clay, pH, organic matters, exchangeable base cations (K+, Na+, Ca2+, Mg2+), cation exchange capacity (CEC) and mineral compositions were significant differences due to different parent materials. During simulated acid rain leaching, BC:Si values of base-uneluted soils were three times more than that of base-eluted soils. Only when the exchangeable base cations adsorbed by soil colloid were eluted can obtain accurate BC:Si values.【Conclusion】The smallest BC:Si value was in humus surface horizon (Ah) in the same soil profile with different soil genetic horizons and the largest BC:Si value was in parent materials horizon (C). BC:Si value of Udic Cambosols derived from different parent materials soils is: Gneiss > Mica schist > Andesite. The mineral proportions of plagioclase, illite, chlorite, and vermiculite in soils controlled the BC:Si values. Therefore, only on the basis of corresponding BC:Si, the response degree of Cambosols with different parent materials to acidification process can be accurately evaluated. The results can provide data support for soil acidification rate evaluation regionally.