Soil salinization exacerbates nitrogen (N) loss in farmland and reduces fertilizer efficiency. The aims of this study were to investigate the effects of exogenous organic acid application on nitrogen transformation, loss pathways, and nitrogen use efficiency in coastal saline soil, and to provide a scientific basis for efficient nitrogen management in salt-affected farmland.A field in-situ monitoring experiment was conducted in coastal mildly saline farmland. Based on conventional fertilization (CKU), three organic acid treatments were established: oxalic acid (OA), compound free amino acids (AA), and fulvic acid (FA). Dynamics of soil inorganic nitrogen content, ammonia (NH?) volatilization and nitrogen leaching losses were systematically monitored, and crop nitrogen uptake and nitrogen use efficiency were determined.Compared with CKU: 1) The OA treatment significantly reduced cumulative NH? volatilization loss and cumulative nitrogen leaching loss by 34.8% and 46.8%, respectively, but had no significant effect on soil inorganic nitrogen content or crop nitrogen use efficiency. 2) The AA treatment significantly increased inorganic nitrogen content in the 0-10 cm soil layer by 96.3% and 87.2% at the seedling and growth stages, respectively. It also significantly enhanced crop nitrogen uptake and apparent nitrogen recovery efficiency by 28.8% and 50.7%. 3) The FA treatment significantly increased inorganic nitrogen content in the 0-10 cm soil layer at harvest by 122.1%. Crop nitrogen uptake and apparent nitrogen recovery efficiency were significantly increased by 28.4% and 50.1%, respectively, while nitrogen leaching loss was significantly reduced by 62.7%.OA and FA treatments were effective in reducing NH? volatilization and nitrogen leaching losses, whereas AA and FA treatments significantly promoted crop nitrogen absorption and improved nitrogen use efficiency. The reduction in NH? volatilization might be related to soil salinity and pH, while the decrease in nitrogen leaching could be associated with an increase in water-stable macro-aggregate content. This study provides scientific data and technical support for utilizing organic acids to mitigate nitrogen loss and enhance nitrogen fertilizer efficiency in coastal mildly saline soils.