Abstract: 【Objective】 To compare the fertilizer efficiency of organic manure replacement in drip irrigation cotton and the difference in soil nitrate nitrogen (N) under nitrogen reduction, so as to select suitable organic manure replacement N technology and improve N utilization rate. 【Methods】 Five treatments were set: (1) No N fertilizer (N₀).(2) Customary fertilization (N₃₀₀).(3) N reduction by 20% (N₂₄₀) under customary fertilization.(4) A 20% N reduction afterwards by conventional fertilization,75% N was provided by urea and 25% N by organic manure (N₁₈₀MN₆₀).(5) Fulvic acid 150 kg/hm² addition (N₁₈₀MN₆₀FA) on the basis of treatment (4).After that, the effects of organic manure replacing N fertilizer on cotton yield and N use efficiency were analyzed. 【Results】 (1) Compared with conventional fertilization, N₁₈₀MN₆₀FA significantly increased cotton biomass and increased yield by 3.3%-6.4%.Cotton biomass and yield of organic manure replaced part of N fertilizer were roughly the same.(2) Compared with conventional fertilization, N₁₈₀MN₆₀ and N₁₈₀MN₆₀FA had no significant difference in N uptake, but the N use efficiency increased by 8.4 and 11.0 percentage points respectively, and the soil N surplus was reduced.(3) Under constant N content, N₁₈₀MN₆₀FA significantly increased soil nitrate N. 【Conclusion】 Under the condition of 20% N reduction, the effect of organic manure replacing part of N fertilizer combined with fulvic acid is better than that of conventional fertilizer, and the effect of organic manure replacing part of N fertilizer is similar to that of conventional fertilizer.