The invention provides a method for preparing AMF (Arbuscular Mycorrhizal Fungus) capsule fungicide. The method is characterized in that sodium alga acid is used as a basic carrier, a mixture is obtained by matching and mixing multiple fillers such as chitosan, gelatin, glycerol, rice, peat, coal cinder and malt sprout in the basic carrier, a fungicide mixture can be obtained by embedding the fungicide in the mixture after the mixture is sterilized, a spherical object can be prepared by dripping the fungicide mixture into calcium chloride solution in a physical extrusion way, and the AMF capsule fungicide can be obtained after the spherical object is solidified and cleaned. According to the method disclosed by the invention, spores, mycorrhiza and hypha of inner glomus intraradices fungus are embedded in the sodium alga acid, a complete infection process can be completed when the spores, the mycorrhiza and the hypha are seeded in unpasteurized soil, and the infection rate can be increased with the prolonging of the infection time. The method disclosed by the invention has the advantages of simpleness, low cost and low toxicity; an embedding material of the AMF capsule fungicide prepared by the invention can be easily decomposed by microorganism, the preservation time is longer, and the AMF capsule fungicide can be simultaneously and directly seeded in a big field.