To compare the effects of single urea and urea combined with slow-release fertilizer application on runoff nitrogen loss, soil nutrients and growth of silage forage maize in slope arable land of Yunnan Province. In the runoff trough experiment under natural rainfall, three treatments of single urea (CK), urea supplemented with the nitrification inhibitor Instant Nortech ^®21 with 40% N replacement + 60% common urea (Treatment I) and polyglutamate Plus 3 with 40% N replacement + 60% common urea (Treatment Ⅱ) were set up under iso-nitrogen conditions according to conventional fertilizer application rates in Yunnan. The results showed that the highest reductions of total N, ammonium N and nitrate N loss concentrations were 2.59, 1.60, 1.42 mg/L and 1.61, 1.38, 1.25 mg/L for treatments I and Ⅱ, respectively, when compared with CK treatment during the fertility period. Compared to CK, the cumulative losses of total nitrogen, ammonium nitrogen and nitrate nitrogen were reduced by 18.56%, 16.19%, 24.31% and 10.75%, 8.73% and 17.08% for treatments I and Ⅱ, respectively. During the growth period of silage maize, the combined application of slow release fertilizer treatment significantly increased the ammonium N content by 13.94%~45.04% and 9.63%~22.39%, significantly reduced the nitrate N content by 3.70% ~29.91% and 8.61%~12.55%, and significantly increased the soil microbial biomass N content by 22.13%~31.76% and 11.80%~22.81%. Urea combined with slow-release fertilizer could also significantly increase the silage yield and plant N uptake, and improve the quality traits of silage maize by significantly increasing the crude protein and crude fat contents and reducing the crude ash and detergent fibre contents of the plant. Correlation analysis showed that runoff N loss was negatively correlated with soil N content, silage maize yield and plant N uptake, soil N was positively correlated with both yield and plant N uptake, and yield was significantly positively correlated with plant N uptake. In conclusion, compared with single urea, urea combined with slow-release nitrogen fertilizer could slow down the nitrification process of soil nitrogen, significantly enhance the nitrogen fixing ability of soil, maintainthe high nitrogen level of soil, and thus improve the yield and quality of silage maize, providing a scientific and theoretical basis for the fertilization of silage maize in red soil slope arable land.