Abstract: The hydrological processes and nitrogen dynamics of a small watershed were studied in a monsoon evergreen broad-leafed forest of Dinghu Shah Biosphere Reserve. The results showed that the hydrology of this forest had distinct characteristics. The nitrogen input by rainfall was 35.57kg·ha-1 and the output in surface runoff was 9.25kg·ha-1 in a year. 4.72kg·ha-1·yr-1 of nitrogen was leached out from the canopy by rain. The nitrogen concentrations in stemflow of different species were different. The regression equations of nitrogen contents in each component of the hydrological cycle and the monthly rainfall were set up.