Agricultural non-point source nitrogen has become the main source of environmental safety in the Three Gorges Reservoir. However, investigation on agricultural non-point source nitrogen pollution has not been studied in depth which agricultural land was the main source, and how to enter Three Gorges Reservoir. Purple soil sloping ploughland in Three Gorges Reservoir was taken as the studied object to explore the effect of ammonia volatilization on nitrogen pollution. The ammonia volatilization characteristics of ammonium bicarbonate, urea and compound fertilizer in typical farming modes, and the nitrogen budget in a small watershed were investigated. The study was conducted by using a paradigm of controlled experiments in situ. The results show that the ammonia volatilization flux of compound fertilizer is the lowest and the change is the most gradual. Meanwhile, the peak value of ammonia volatilization flux of urea lags behind and decreases slowly, while that of ammonium bicarbonate appears earlier and decreases faster. The ammonia volatilization loss ratio of urea, ammonium bicarbonate and compound fertilizer in the watershed are 8.82%~18.37%, 17.86%~30.70% and 2.56%~3.86%, respectively. Besides, the ammonia volatilization loss ratio is in order:ammonium bicarbonate > urea > compound fertilizer, and the ammonia volatilization loss ratio between typical land use is in order:paddy field > fruit forest > dry land. Moreover, it is found that chemical fertilizer and ammonia volatilization are the most important nitrogen inputs and outputs in the watershed, and soil nitrogen residues are serious, which increases the risk of nitrogen loss. From the perspective of environmental friendliness, reducing the frequency of ammonium bicarbonate use, reducing the amount of fertilizer applied to dry land and fruit forest, and optimizing the application structure of nitrogen fertilizer in the Three Gorges Reservoir are effective ways to reduce ammonia volatilization. The reduction of ammonia volatilization is of great significance for the prevention and control of nitrogen pollution in the Three Gorges Reservoir.