In order to correctly understand the control effect of grass cover on non-point source pollution and promote the construction of ecological orchard, a research was carried out to study the effects of cover crop (Vulpia myuros) on the accumulation and runoff loss of nitrogen. Three management modes, including grass cover on soil surface until withering (Cov), grass removed (Rem), and cleaning tillage as control (Cle). The results showed that the content of mineral nitrogen in the soil surface (0-1 cm) of the Cov treatment was 2.6 and 4.5 times as high as that of the Rem and Cle treatments when the withered grass degraded quickly (in September), respectively. At the same time, the Cov treatment increased the concentration of mineral nitrogen in the runoff by 42.6% and 20.9%, respectively. The Cov treatment decreased the rain runoff by 88.3-98.7%, and increased the rain leakage by 42.1-97.6% when compared with the Cle treatment. The results of three rainfall events showed that the runoff loss of mineral nitrogen was 90% lower than that of the clean tillage, and deep layer (25 cm) leakage was increased by 89.6%. In conclusion, planting grass and covering it on the soil surface in orchard is an advantageous management to prevent non-point source pollution by reducing nitrogen loss through runoff.