The invention discloses a preparation method of biostimulant and application thereof. The preparation method comprises the following steps of selecting 3% to 5% of EM (
effective microorganism) raw liquid, 2% to 5% of
carbon source, 5% to 10% of 20%
calcium-
magnesium-
phosphor fertilizer suspension, 0.5% to 1% of
nitrogen source, and 79% to 89.5% of
chloride-
free water, and uniformly mixing; puttinginto a rocking
bed, fermenting for 5 to 7d at the temperature of 35 to 37 DEG C in an anaerobic way, standing, and filtering to separate
solid and liquid; concentrating filtrate for 35 to 60 min at the pressure of -1.5 to -0.5 MPa, and spray-
drying the concentrated liquid, so as to obtain the biostimulant. The biostimulant has the advantages that the
calcium-
magnesium-
phosphor fertilizer and theprotein
powder which are difficult to dissolve into water are converted into chelating
calcium and
magnesium, small-molecular
amino acid and organic
phosphor which are water-soluble, so that the absorbing and utilization efficiency of calcium, magnesium and mineral nutrients is improved, and the physiological barriers caused by lack of calcium, magnesium and the like in plants can be effectively solved, such as tomato blossom-end rot and
chlorosis of
green pepper; by irrigating to roots, the physicochemical property of the soil is improved, and the
soil water retention effect and nutritional element activation effect are better.