The invention discloses a soil improvement agent with a sterilizing effect. Starch, plant ash, dried poultry manure, corn straw, rapeseed slag, jerusalem artichoke extract, glycine, chitosan, and a fermentative microbial agent are used as main ingredients, and thiourea, montmorillonite, bamboo fibers, charcoal, polylactic acid fibers, polyamide fibers, sodium polyacrylate, calcium hydroxy phosphate, sodium hypochlorite, manganese chloride, barium hypochlorite, magnesium sulfate, a stabilizer and an antioxidant are added as raw materials to prepare the soil improvement agent with the sterilizing effect. The soil improvement agent can effectively improve soil property, reduces pathogenic bacteria in soil, and is pollution-free to the environment. Meanwhile, the invention further discloses a preparation method of the soil improvement agent with the sterilizing effect.