[Objective] The soil improvement potential of oat （Avena sativa） biological sand barriers in the restoration of alpine sandy land were evaluated in order to clarify their regulatory mechanisms on soil carbon （C）， nitrogen （N）， and phosphorus （P） nutrients and their ecological stoichiometric characteristics during a two-year planting period， and provide theoretical and practical guidance for the ecological restoration of desertified grassland in alpine regions. [Methods] Typical alpine mobile sand dunes in Qinghai Lake basin were selected as the study area， where oat biological sand barrier plots were established. Soil samples were collected at four key time points over a two-year continuous growing period： before sowing （T₁）， at the end of the first growing season （T₂）， at the beginning of the second growing season （T₃）， and at the end of the second growing season （T₄）. Soil carbon， nitrogen， phosphorus contents and their ecological stoichiometric characteristics were determined at different growth stages. [Results] The oat biological sand barriers significantly increased the soil organic carbon （SOC） and total nitrogen （TN） contents in the surface soil （0—20 cm）， while the increase in total phosphorus （TP） was relatively slow. In the T₄ period， the SOC and TN in the surface soil increased by approximately 18.2% and 29.3%， respectively， compared to the T₁ period， and the SOC and TN in the deep soil （20—40 cm） increased by 56.8% and 27.0%， respectively. The available nitrogen （AN） and available phosphorus （AP） contents in the surface soil increased by 19.8% and 72.7%， respectively， in T₄ compared to T₁， while soil pH value decreased by approximately 15.0%. With increasing planting duration， the C/N and C/P ratios showed a trend of first increasing and then decreasing， while the N/P ratio showed a gradually increasing trend. Mantel test results indicated that SOC， TN， TP， and pH value were the main factors influencing the stoichiometric characteristics. [Conclusion] The oat biological sand barriers effectively enhance soil organic matter level and nutrient supply， promoting the cycling of elements. Additionally， they optimize the ecological stoichiometric structure of C， N， and P， alleviate nutrient limitations， and enhance soil ecological functions. Furthermore， the restoration benefits accumulate progressively over the two-year planting period， demonstrating potential for long-term soil quality restoration.