It has low rainfall，high evaporation and low soil fertility in the Loess Plateau. The effects of different mulching measures on soil nitrogen，nitrogen storage and enzyme activity in spring wheat farmland were investigated，which of great significance to improve nitrogen utilization efficiency and reduce nitrogen loss. This experiment was based on the positioning experiment of spring wheat continuous cropping with different coverage measures，which began in 2016，with corn straw strip mulching(SM)and plastic full mulching(PM)，and no mulching(CK)as control. The spatiotemporal distribution of soil total nitrogen，ammonium nitrogen，nitrate nitrogen，microbial biomass nitrogen，urease，catalase，nitrate reductase，and nitrite reductase activities in the 0–20，20–40，and 40–60 cm soil layers during the 2019 harvest period，2020 flowering and harvest periods were studied and the soil nitrogen storage were calculated. SM treatment increased the contents of nitrogen strorage，inorganic nitrogen，microbial biomass nitrogen，nitrate reductase activity，catalase activity，and urease activity in topsoil(0-20 cm)by 33.72%，23.42%，19.10%，10.95%，16.90% and 76.05%，respectively，while SM treatment decreased the activity of nitrite reductase. PM treatment increased inorganic nitrogen content，nitrate reductase activity and catalase activity by 22.46%，7.26%，20.56%，respectively，but the soil nitrogen storage，microbial biomass nitrogen，urease activity and nitrite reductase activity were decreased. The activity of soil nitrogen invertase directly affected the conversion rate of nitrogen，and the enzyme helped to maintain the dynamic balance between different forms of nitrogen in the soil. Straw strip mulching effectively improved soil total nitrogen and nitrogen components and nitrate reductase，catalase，urease activity，reduced nitrite reductase activity. Urease and nitrate reductase were key enzymes in the nitrogen cycle，and they worked together to improve the effectiveness of nitrogen and the stability of total nitrogen. Catalase improved microbial activity by changing soil microenvironment and indirectly affects total nitrogen content. Nitrite reductase reduced the accumulation of nitrite nitrogen and promoted the fixation and transformation of nitrogen in the nitrogen cycle. Straw strip mulching effectively increased soil nitrogen storage，improved soil nitrogen supply capacity and improved soil fertility level by changing the activity of related enzymes.