The authors have conducted ca.1-year observations at Guiping, Gaoyao and Qingyuan stations of the Pearl River system, and the main ions (F<SUP>-, Cl-, NO-3, SO2-4, Na+, K+, Mg2+ and Ca2+) and some selected trace elements (Rb and Sr) of the river water were reported here. Similar trends of Rb/Na variations were observed in all these stations, with higher Rb/Na occurring during summers and autumns and lower during winters, suggesting that silicate weathering was enhanced during summers and autumns, and relatively weaken during winters. Warm and humid climate, as well as enhanced organic material decays during summer and autumn favors chemical weathering. While the variations of carbonate weathering were different in these stations, suggesting more complicated controls for carbonate weathering.