Rainfall partitioning is an important pathway of the cycling of base cations in forest ecosystems, as base cations can be rapidly transferred from forest canopy to forest floor along with throughfall and stemflow, replenishing nutrients to soils. These processes can be greatly affected by forest transformation through, for example, altering the structure of forest canopy, but how forest transformation may affect the fluxes of base cations along with rainfall partitioning is rarely addressed in the literature. To evaluate the impacts of forest transformation on base cation cycling with rainfall partitioning, we monitored the concentrations and fluxes of four common base cations, namely potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and sodium (Na⁺), of rainfall, throughfall, stemflow, and surface runoff in four types of subtropical forests (Castanopsis carlesii natural forest, C. carlesii secondary forest, C. carlesii plantation, and Cunninghamia lanceolata plantation) after forest transformations during the period from April 2021 to March 2022. The results showed that (1) the amount of throughfall, stemflow, and surface runoff varied significantly among different forest types under essentially the same rainfall conditions; (2) K⁺, Ca²⁺, and Mg²⁺ were leached in the canopy, while Na⁺ was absorbed in the canopy during the oneyear study period; (3) the net throughfall flux (NTF) of K⁺ and Na⁺ were the largest in the C. carlesii natural forest, while the NTF of Ca²⁺ and Mg²⁺ were the largest in the Cun. lanceolata plantation, and base cations of the NTF were smaller in C. carlesii secondary forest and C. carlesii plantation. Overall, the transformation of C. carlesii natural forest to C. carlesii secondary forest and C. carlesii plantation reduced the NTF of base cations and increased the fluxes of base cations in surface runoff, which may pose a risk of declining the ecological service functions of C. carlesii secondary forest and C. carlesii plantation.