The invention provides a preparation method of a soil amendment and a soil amendment. The method includes: mixing a
cellulose degradation inoculant with a
fermentation substrate evenly and performingcomposting
fermentation, and in the first
fermentation process, rapidly heating a
pile body to quickly degrade lignocelluloses substances in the substrate; when the temperature of the
pile body startsto drop, using a first functional inoculant and wood vinegar for second fermentation of the
pile body; rapidly heating the pile body subjected to second fermentation again, when the temperature of the pile body starts to drop again, adding a second functional inoculant,
chitosan and alginate
oligosaccharide, and carrying out third fermentation in cooperation with pile turning and stirring. The method carries out substrate fermentation in three stages, can improve the fermentation efficiency and make the fermentation more sufficient, the pile body is heated repeatedly, and grass seeds, parasite eggs and pathogenic microorganisms can be killed thoroughly. After application of the soil amendment, the utilization efficiency of soil
nutrient elements is increased, and the
soil quality is improved, the soil amendment also has
growth promotion,
insect resistance and other functions, and is economical and environment-friendly.