Freshwater resources are scarce in arid regions, and the rational use of brackish water resources can alleviate local freshwater shortages, but long-term brackish drip irrigation increases the risk of soil salinization, which in turn affects soil nutrient transformation and microbial diversity. Soil phosphorus availability is critical for crop growth, yet it is unclear how long-term brackish drip irrigation will affect soil phosphorus transformation. Therefore, to investigate the effects of long-term brackish drip irrigation on soil phosphorus-transforming microorganisms and their functional genes in cotton fields, the experiment was set up with two irrigation water salinities, freshwater （0.35 dS·m