The invention relates to a fulvic acid and rhizobium biological type leguminous plant seed coating agent and a preparation method thereof. The fulvic acid and rhizobium biological type leguminous plant seed coating agent is characterized by comprising fulvic acid, a rhizobium culture solution, a film forming agent, trophic factors and the balance of water as raw materials. The preparation method comprises following steps of: adding 5-8% of film forming agent into the balance of water, and heating to 75-85 DEG C to slowly dissolve the film forming agent; then, adding 3-5% of dispersing agent, and adding 0.5-1.0% of trophic factors after the dispersing agent is dissolved; adding 0.03-1.0% of fulvic acid, and cooling to 28 DEG C or so; and finally, adding 3-5% of rhizobium culture solution, and uniformly mixing to obtain the product of fulvic acid and rhizobium biological type leguminous plant seed coating agent. The product has the advantages and effects of promoting the growth of rhizobia, enhancing stress resistance, obviously increasing the survival rate of rhizobia and the competitiveness of pannonibacter phragmitetus, reducing the use amount of chemical fertilizers and pesticides, protecting the environment, improving product quality and ensuring food safety.