Abstract: 【Objective】 To study on the characteristics of biochar from cotton straw aged with dry-wet alternation, freeze-thaw cycle, citric acid, and explore the effects of aging cotton stalk charcoal on ammonia volatilization from sand soil with a view to providing theoretical basis for the utilization of cotton stalk charcoal and its long-term effects on soil improvement in arid areas. 【Methods】 Cotton straw biochar was taken as the test material, three aging methods of dry and wet alternation, freezing and thaw cycle and citric acid were set to analyze the surface morphology of cotton straw carbon and analyze the surface morphology, specific surface area and pore size, pH value, electrical conductivity and other physical and chemical properties of cotton stalk charcoal before and after aging.Meanwhile, the effects of aged cotton stalk charcoal on ammonia volatilization rate and ammonia volatilization accumulation in soil were studied by indoor static soil culture experiment. 【Results】 (1) Compared with fresh cotton stalk charcoal, the pH value, electrical conductivity, total phosphorus and total potassium contents of aged cotton stalk charcoal all decreased and its degree of citric acid was greater than those of dry-wet alternation and freeze-thaw cycle.The specific surface area, total pore volume and mesoporous volume of citric acid of aged cotton stalk charcoal increased by 1.88,1.37 and 1.36 folds, respectively and the average pore size decreased by 0.19 times (P> 0.05).The specific surface area of dry-wet and freeze-thaw aged cotton stalk charcoal decreased significantly, but the average pore size increased significantly.(2) In the whole culture process, the cumulative amount of ammonia volatilization was reduced by 7.4%~34.7% compared with the treatment of fresh cotton stalk charcoal. 【Conclusion】 Three aging modes of freeze-thaw cycle, alternation of wetting and drying, and citric acid change the characteristics of cotton stalk charcoal, inhibit ammonia volatilization in aeolic soil, which is beneficial to soil nitrogen fixation.The citric acid aged cotton stalk charcoal has the best inhibition effect on ammonia volatilization in soil.