The vast area of saline-alkaline grasslands in the agro-pastoral ecotone of northern China has important production and ecological functions. Nitrogen (N) deposition changes the function and structure of vulnerable grasslands. However, the impacts of N deposition on ecosystem multifunctionality (EMF) remains unknown. To address this issue, a three-year in-situ study was carried out between 2018 and 2020 to assess the direct impacts of N addition on grassland ecosystem function. Eight N addition levels were applied: 0, 1, 2, 4, 8, 16, 24, and 32 g·N·m