The invention relates to a preparation method of fast-growing frankia powder. The method comprises the following steps: S1, breeding a frankia strain; S2, treating the pure frankia strain, obtained instep S1, by using a gene mutagenesis method to obtain a fast-growing frankia strain; S3, inoculating the fast-growing frankia strain, obtained in the step S2, into sterilized fermented raw materialsin a fermentation tank to form a bacterial culture material, and carrying out fermenting cultivation on the bacterial culture material to form hyphae; S4, further differentiating the hyphae, obtainedin the step S3, into spores, and eluting with sterile water to obtain bacterial liquid; adding sterile activated carbon into the bacterial liquid for adsorbing the spores, and separating the spore-containing activated carbon from the liquid after the spore adsorption is completed so as to obtain thallus taking the activated carbon as a carrier; S5, enabling the thallus, obtained in the step S4, tobe subjected to freeze-drying treatment by using a vacuum freeze-drying method so as to obtain the bacterial powder. The preparation method, provided by the invention, of the fast-growing frankia powder is good in inoculation effect, rapid in growth speed and suitable for large-scale industrial production.