NOVELTY - A soil modifier comprises first-stage modifier and second-stage modifier. The first-stage modifier comprises calcium nitrate and microorganism preparation. The second-stage modifier comprises microorganism preparation, magnesium nitrate and zinc sulfate. The microorganism preparation is prepared by crushing soybean pulp and corn stalks, microbial fermenting and drying. The microorganism is Chromatium minutissimum, Acidithiobacillus ferrooxidans, Bacillus subtilis, Pichia pastoris and/or Paracoccus pantotrophus.    USE - Soil modifier.    ADVANTAGE - The soil modifier regulates soil microenvironment, improves growing environment of crops, increases crop yield and avoids environmental pollution.    DETAILED DESCRIPTION - A soil modifier comprises first-stage modifier and second-stage modifier. The first-stage modifier comprises 1-10 pts. wt. calcium nitrate and 90-99 pts. wt. microorganism preparation. The second-stage modifier comprises 65-84 pts. wt. microorganism preparation, 6-15 pts. wt. magnesium nitrate and 10-20 pts. wt. zinc sulfate. The microorganism preparation is prepared by crushing soybean pulp and corn stalks, microbial fermenting and drying. The microorganism is Chromatium minutissimum, Acidithiobacillus ferrooxidans, Bacillus subtilis, Pichia pastoris and/or Paracoccus pantotrophus. INDEPENDENT CLAIMS are included for:    (1) preparation of soil modifier comprising crushing soybean and corn stalks, adding water and microorganism fermentation bacterial strain, drying to obtain microorganism preparation, uniformly mixing microorganism preparation and calcium nitrate to obtain first-stage modifier, and uniformly mixing microorganism preparation, magnesium nitrate and zinc sulfate to obtain second-stage modifier; and    (2) application method of soil modifier comprising setting farm without changing farming patterns, stirring tillering fertilizer and 3-5 kg/acre first-stage modifier, reducing amount of fertilizer and mixing with 0.3-0.5 kg/acre second-stage modifier.