Abstract: In order to promote the use of unconventional water and relieve the pressure of agricultural water,the alleviating effect of biochar on the adverse effect of brackish water irrigation is explored. Through the experiment of barrel planting corn in rain shelter,three biochar application gradients of 0%,2% and 5% and the salinity of fresh water,4,5 and 6 g/L irrigation water are set to determine the soil electrical conductivity（EC）,the contents of major salt ions(Na⁺,Ca²⁺,Mg²⁺,K⁺,Cl^-)and the distribution of soil particle size in different treatment stages. The effects of biochar and brackish water irrigation and their coupling on soil salt content and aggregate structure are systematically studied. The results show that:（1） Brackish water irrigation will cause soil salt accumulation,and the application of biochar can effectively reduce the soil EC value,among which 2% biochar has the best effect.（2） The changes in major salt ions in soil during the whole growth period of maize are basically the same under brackish water irrigation. Applying biochar in soil can reduce the content of soil main salt ions,but biochar cannot play an effective mitigation role when the salinity of irrigation water is high（6 g/L）.（3） Brackish water irrigation will destroy soil aggregate structure,and the greater the salinity of irrigation water,the greater the impact. The application of biochar can increase the number of soil water stable aggregates and alleviate the damage of brackish water irrigation to soil aggregate structure,and the application amount of 5% biochar has the best improvement effect. In general,2% and 5% biochar can effectively improve the soil environment under 4g/L brackish water irrigation,which serves as a reference for the development and utilization of brackish water resources.