The invention discloses a saline-alkali soil improver which comprises the following raw materials in parts by weight: 40-80 parts of ardealite, 10-30 parts of rectorite, 20-40 parts of fermented wormwood plants, 10-20 parts of ficus tikoua bureau stems, 30-50 parts of germ bran, 20-30 parts of anion-state nano carbon silicon solution, 20-30 parts of sodium alginate, 6-10 parts of chrysanthemum, 2-8 parts of Chinese honeylocust fruit, 2-6 parts of folium mori, 2-6 parts of radix isatidis, 4-8 parts of sweet potato powder and 4-10 parts of egg shell powder. A preparation method of the saline-alkali soil improver comprises the following steps: (1) preparing the fermented wormwood plants; (2) preparing the ardealite powder and drying the ficus tikoua bureau stems; (3) preparing the rectorite powder; (4) preparing a Chinese herbal medicine mixture; and (5) mixing, granulating and mixing. The saline-alkali soil improver disclosed by the invention is suitable for improving the saline-alkali soil of the northeast China, reduces the soil alkalinity, improves the soil desalting rate, neutralizes the soil acidity and alkalinity, improves the soil fertility, enhances the disease resistance of corn crops, promotes the growth of the corn crops and boosts the agricultural economy.