The variation characteristics of soil nitrogen in different planting patterns of winter wheat and alfalfa were studied in order to provide reference for different planting patterns of grain and grass. Based on field experiments started in Southwest Shanxi in2014，crop yield and soil profile nitrogen characteristic ofwheat，alfalfa monoculture and wheat -alfalfa intercropping were studied in 2017 and 2018. The results showed that:(1)In the two experimental years，the biomass of wheat-alfalfa intercropping increased，and the nitrogen contents of stem，leaf and grain of wheat were higher than those of wheat monoculture. Compared with any monoculturesystem，the nitrogen accumulation of wheat -alfalfa intercropping system was increasedsignificantly.(2)Nitrogen content in surfacesoil(0～30cm)was affected by planting pattern. In spring，the nitrogen content in alfalfa monoculture was higher than those of wheat monoculture and wheat-alfalfaintercropping；At wheat harvest，the nitrogen contents in wheat monoculture and wheat -alfalfa intercropping was higher than that of alfalfa monoculture. Nitrate nitrogen content in soil profile of 200 cm depth during the growth period of fallow alfalfa in wheat field was asfollows:wheat monoculture>wheat -alfalfa intercropping>alfalfa monoculture.At different growth stages，nitrate nitrogen in wheat monoculture was leached vertically in soil profile and accumulated in deep soil，however，wheat -alfalfa intercropping alleviated the vertical leaching of nitrate nitrogen.(3)Ammonium nitrogen of alfalfa monoculture in 0～ 30 cm soil layer was slightly higher than that of wheat monoculture and wheat-alfalfa intercropping in the next spring. The content of ammonium nitrogen in wheat monoculture system in different sections of fallow alfalfa growing period at 200 cm soil depth was lower than that of alfalfa monoculture and wheat-alfalfa intercropping.(4)The soil inorganic nitrogen of wheat -alfalfa intercropping accumulated in the winter period(October of the previous year -March of the nextyear). During the symbiosis period of wheat andalfalfa(March -June)，soil inorganic nitrogen was in the consumptionstage；After wheat harvest(June -October)，the inorganic nitrogen of single alfalfa was supplemented. In conclusion，compared with any monoculture，wheat -alfalfa intercropping system improved the soil and crop nitrogenlevels，and reflected the advantages of wheat -alfalfa intercropping system.