Abstract: Based on stationary observation and chemical analysis in tropical mountain rainforest watershed at Jianfengling of China for five years,the hydrochemical cycling in the ecosystem was studied systematically combined with their hydrologic process. The distribution of mean rainfall with 2 668.3 mm per year was that 46.7% of rainfall was runoff,and 53.3% of rainfall was evaporated by the system, and 14.0% of rainfall was intercepted by forest canopy. The total amount of N,P,K,Ca and Mg in precipitation was 78.36 kg/(hm2·a)and that in runoff was 56.72 kg/(hm2·a),so the net accumulation of them in the system was 21.6 kg/(hm2·a). The total amount of Si Org-C, Al, Mn in rainfall was 24.99 kg/(hm2·a)and that in runoff was 112.28 kg/(hm2·a),so they were loss elements of water cycling in the system. The ecosystem was at its regenerating progress phase. The chemical leaching of the canopy layer combined with rainfall process was proved with the leaching efficiency of 4.11. The regression between chemical element and water of the hydrologic elements was put forward in the paper.