In order to investigate the effects of different slope gradients (5°

8°

15° and 25°) and rainfall intensities (60

90

120 and 150 mm/h) on TN (total nitrogen) loss in surface runoff and subsurface flow

an artificial simulated rainfall experiment was conducted

and decomposed granite soil was taken as the experiment object. As the test design

the rainfall duration was 90 min after the appearance of surface runoff

and the test ended up when the subsurface flow disappeared. The results showed that: (1) The loss concentrations of TN in surface runoff declined rapidly at the early stage

and increased with the reduction of rainfall intensity and the increasing of slope gradient

and then tended to be stable. (2) The loss concentrations of TN in subsurface flow were significantly higher than those in surface runoff

and the curves of TN loss concentration in subsurface flow all followed a law of “rising-falling-slightly rising-steady”. Generally

the loss concentrations increased with the reduction of rainfall intensity and the increasing of slope gradient. (3) The total losses of TN in surface runoff and subsurface flow were both increased with the increasing of rain intensity and slope gradient. Subsurface flow was the main approach of TN loss on slope

and its proportion could reach 91.26% to 99.61%. The proportion of TN loss in surface runoff increased with the enhancement of rainfall intensity. (4) Rainfall intensity and runoff volume were both extremely significantly positively related to the TN loss in surface runoff and subsurface flow

while slope gradient only significantly positively correlated with the TN loss in subsurface flow. (5) There was a critical rainfall intensity between 90 mm/h and 120 mm/h

over which

the TN loss in surface runoff and its proportion in total loss would sharply rise.