The oasis is a unique ecosystem in arid regions. Currently, there is a comprehensive understanding gap regarding the community characteristics of the entire nitrogen cycling microorganisms in oasis soil, including species diversity, community structure, and nitrogen functional traits, as well as their influencing factors. To elucidate the influence of oasification on nitrogen metabolism in agricultural soils, this study examines the intricate variations in microbial composition and gene abundances related to nitrogen metabolism in cotton field soils with varying cultivation histories (ranging from native deserts to 30-year-old cotton fields) in the Aral Reclamation Area of Xinjiang, China. The study findings reveal: As oasification intensifies, (1) agricultural practices such as irrigation and fertilization result in increased soil moisture and nutrient levels, with total nitrogen (TN), NH4 +-N, and NO3 --N showing particularly significant increases. (2) The primary nitrogen cycling process shifted from dissimilatory nitrate reduction (DNRA, 29.38%-37.64%) to denitrification (DEN, 31.67%-52.92%), indicating that denitrification becomes the dominant process in oasification. (3) Soil organic carbon (SOC), soil moisture (SWC), and phosphorus content (TP) significantly influence nitrogen metabolism-related functional species and genes. This study sheds light on the complex effects of oasification on microbial nitrogen metabolism processes in farmland, and explores the mechanism of nitrogen metabolism by coupling the changes of functional microbial communities and genes related to nitrogen metabolism.