By analyzing the chemical compositions of river waters, rain waters, surface sediments, and rocks of large river catchments in China, combining with hydrological information, this paper uses the forward model to assess the chemical weathering rates, capacity and mechanism of the atmospheric CO2 consumption and then discusses the behaviors of chemical weathering under various conditions including climate, lithology, topography, and vegetation. The study also provides reference and basic information for selecting of sites and mineral types for CO2 capture and storage in China. By comparing the characteristics of chemical weathering in some small river catchments draining the typical silicate rock regions, the study finds that the Nandujiang River, which flows on basalt formations in tropical climate zone,has the highest silicate weathering rates (7.2×105 mol/km2a), which is close to those rivers in New Guinea near the equator.