In order to study the effect of amendments on infiltration characteristics and water and salt distribution of saline-alkali soil in Hetao Irrigation District, soil column experiment was carried out under five experimental conditions: control group and two contents (1% and 2%) of two modifiers (biochar and desulfurized gypsum). The results showed that: (1) Compared to the control group, 1% biochar made the infiltration time delay 8.9%, inhibited water infiltration, and reduced the amount of cumulative infiltration on the same time, while 2% biochar firstly inhibited and then promoted the process of infiltration, and it made the infiltration time shortened by 35.6%. Both desulfurized gypsum made the infiltration time shortened by 91.1%. They effectively promoted water infiltration and increased the amount of cumulative infiltration on the same time; Only 2% biochar significantly increased the final cumulative infiltration by 62.7%. (2) There was a power function relationship between the migration distance of wet front and time. Kostiakov model described the relationship between cumulative infiltration and time better than Philip model. (3) Compared to the control group, only 1% biochar reduced the soil moisture content by 2.7% after infiltration, while the other treatments had varying degrees of increase. The two application rates of biochar significantly reduced the soil salt content by 28.5% and 52.0%, respectively. However, the two contents of desulfurized gypsum significantly increased the soil surface salt content by 184.3% and 403.7%, respectively. The 2% application rate significantly increased the overall average soil salt content by 73.0%. By comprehensive consideration of the infiltration characteristics, soil moisture content and desalting effect of each treatment, biochar under the content of 2% is more suitable to improve saline-alkali soil in Hetao Irrigation District.