【Objective】The soil acidification rate in current environment is the basis for controlling soil acidification. However, the accurate estimation of soil acidification rate is difficult due to the buffer effect of soils. The soil consumes exogenous H+ and releases base cations through mineral weathering (compensating for base cations loss and inhibiting soil acidification) and the cation exchange process (increasing exchangeable H+ and inducing soil acidification). Nevertheless, it is difficult to distinguish these processes, which leads to large errors in estimating soil acidification rate. Since silicon (Si) only comes from mineral weathering reaction and has nothing to do with cation exchange, the stoichiometry of base cations (BC: K+, Na+, Ca2+, Mg2+) and silicon release (BC:Si) during soil mineral weathering can quantify the H+ consumed through mineral weathering, which is helpful to determine accurate soil acidification rate. 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. To avoid the influence of the base cations adsorbed by soil colloid on stoichiometry of the mineral weathering process, soil exchangeable base cations were washed by elution experiment. Then, the release of base cations and silicon of soils derived from three parent materials were obtained by leaching of simulated acid rain. 【Result】The results showed that content and distribution in the profile of clay, pH, organic matters, exchangeable base cations (K+, Na+, Ca2+, Mg2+), cation exchange capacity (CEC) and mineral compositions were significantly different for 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. The smallest BC:Si value was in the humus surface horizon (Ah) in the same soil profile with different soil genetic horizons and the largest BC:Si value was in the parent materials horizon (C). BC:Si value of Udic Cambosols derived from different parent materials soils followed: Gneiss > Mica schist > Andesite. The mineral proportions of plagioclase, illite, chlorite, and vermiculite in soils controlled the BC:Si values. 【Conclusion】Therefore, only on the basis of corresponding BC:Si, the response degree of Cambosols with different parent materials to the acidification process can be accurately evaluated. The results can provide data support for soil acidification rate evaluation regionally.