In order to investigate the effects of forage intercropping and nitrogen application on soil characteristics and forage yield in the southern foothill of Yinshan，Inner Mongolia，a field plot trial was conducted in 2020 to 2021 based on the forage oat and common vetch，and three planting patterns（OV：intercropping of oat and common vetch；MO：monoculture oat； MV：monoculture common vetch）and three nitrogen application levels（N0：0 kg/hm² ；N75：75 kg/hm² ；N150：150 kg/ hm² ）were set up. The changes of soil nitrogen content，soil available nutrients content and forage hay yield under different planting patterns and different nitrogen application rates were studied. The results showed that the soil total nitrogen content showed an increasing trend with the increase of nitrogen application rate，and the soil total nitrogen content was increased by intercropping compared with single cropping. The soil total nitrogen content of OV-N75 was the highest among all treatments， which was increased by 50.89% and 4.76% compared with N0 in two years，respectively. Soil alkali-hydrolytic nitrogen content showed an increasing trend with the increase of nitrogen application rate，and reached the highest at N150 level，and OV-N150 treatment had the highest value，which was 9.54% and 29.15% higher than that of N0 in two years，respectively， but had no significant difference with N75 level（P＞0.05）. Intercropping combined with nitrogen application increased soil nitrate nitrogen content，and OV-N150 treatment was the highest，which was 113.60% and 119.64% higher than N0 in two years，respectively. The soil ammonium nitrogen content in MV mode was the highest，and the nitrogen level in N150 was the highest，which was 18.13% and 69.37% higher than that in N0 in two years，respectively. Under different nitrogen application levels，the soil pH of the three planting modes was MO＞MV＞OV，and the soil pH of OV-N75 treatment in 2020 was the lowest，which was 0.38%-3.40% lower than that of other treatments. Nitrogen application was beneficial to increase soil organic matter content，and MV-N150 treatment had the highest soil organic matter content，which was 14.45% and 9.70% higher than that of N0 and N75 in 2020，and 32.54% and 6.23% higher than that of N0 and N75 in 2021. The soil available phosphorus content showed an increasing trend with the increase of nitrogen application rate，and reached the highest value in N150 treatment，but had no significant difference with N75（P>0.05）. The content of OV-N75 treatment increased by 11.31% and 29.73%，respectively，compared with N0. Nitrogen application significantly increased soil available potassium content compared with no nitrogen application，but there was no significant difference in N75 and N150 levels（P>0.05），and OV-N75 treatment was 7.57% and 24.12% higher than OV-N0 treatment in two years，respectively. The effects of nitrogen application level on soil microbial biomass carbon and nitrogen contents were significant（P<0.01）. Intercropping combined with nitrogen application increased soil microbial biomass carbon and nitrogen content，and the OV model had the highest microbial biomass carbon content，which was 76.16% and 71.72% higher than that of N0 in two years under N75 treatment，respectively. MV mode showed the highest soil microbial biomass nitrogen content，and N75 treatment increased by 217.56% and 184.28% compared with N0 in two years，respectively. The hay yield of oat and common vetch under different cropping modes showed an increasing trend with the increase of nitrogen application rate. The hay yield of N150 treatment was the highest，and the 2-year hay yield of N75 was increased by 29.41% and 27.54%，and that of N150 was increased by 36.60% and 51.21% compared with N0，respectively. In conclusion，the intercropping oat and common vetch model could improve the forage diversity，soil nitrogen content and available nutrient content in this region，and there was no significant difference between the intercropping oat and common vetch under 75 and 150 kg/hm² nitrogen application condition（P>0.05），which was more suitable for promoting planting in the southern foothill of Yinshan Mountain.