In this study, soda saline-alkali soil in Horqin Banner, Inner Mongolia was selected as the research object with 3 soil quality grades (medium, good and excellent) and 5 forage crop species (Gaodan grass, barnyard grass, silage corn, Hunan millet, sweet sorghum) to study the effects of forage crops on soil salinization and alkalinization and nutrient contents, and soil improvement effects were evaluated according to the fuzzy matter-entropy weight model. The results showed that average soil pH after crop harvest decreased by 1.64% but not significantly different compared with that before crop sowing, while EC, total soluble salt and alkalinity degree significantly decreased (P<0.05). Different forage crops decreased Ca²⁺, Mg²⁺, HCO₃^-+CO₃^2- contents while increased soil K⁺+Na⁺, Cl^- contents, while had different effects on SO₄^2- content. After harvest, alkali-hydrolyzed nitrogen and available potassium contents decreased by 15.15% and 24.06%, respectively, compared with those before crop sowing. Fuzzy matter-entropy weight model showed that silage corn had better improvement effect on soil with higher salinization while sweet sorghum and Gaodan grass were more suitable for soil with less salinization. Soil salinization and alkalization parameters were more affected by salt ion concentration than soil nutrient index. Available potassium was positively correlated with total soluble salt, alkalization degree and EC (P<0.05), indicating that the increase of saline-alkali index promoted the accumulation and transformation of available potassium to a certain extent. In conclusion, forage crops are feasible for soda saline-alkali soil improvement with a certain effect in inhibiting soil salinization.