In order to investigation the inhibition effect of Artemisia argyi powder (a by-product of Artemisia argyi var. argyi 'Qiai' made of moxa) on plant pathogenic fungi and the potential to develop botanical fungicides. Artemisia argyi powder had been extracted by water, 50% ethanol, ethanol, ethyl acetate and petroleum ether, the fingerprints of different solvent extracts were established to compare the differences. Meanwhile, the antibacterial activity of different extracts was tested to screen the strongest antifungal active parts in A. argyi powder. In addition, the virulence equation and EC50 value of ethyl acetate extract against 9 kinds of plant pathogenic fungi such as Magnaporth grisea were determined by mycelial growth rate method. Finally, the morphological changes of the colonies were observed, and the hyphae microscopic structure and spores were observed by fluorescence inverted microscope. The results showed that polar solvents (ethyl acetate, ethanol and water) had higher extraction rate for A. argyi powder than non-polar solvents (petroleum ether), and there were great differences in the properties and components of the five solvent extracts. Among them, the fingerprints of pure ethanol extract and ethyl acetate extract are similar, and the main components are kaempferol, jaceosidin, eupatilin and other flavonoids. The antibacterial activities of five solvent extracts of A. argyi powder against plant pathogenic fungi were as follows: ethyl acetate > ethanol > 50% ethanol > petroleum ether > water. The ethyl acetate extract of A. argyi powder had significant inhibitory effect on a variety of plant pathogenic fungi,especially on Sclerotium rolfsii, Magnaporth grisea, Gloeosporium theae-sinensis, Alternaria alternata and Cercospora nicotianae, with EC50 values of 1.63, 2.88, 3.38, 5.73 and 5.77 g / L, respectively. Moreover, ethyl acetate extract can also affect the growth and development of plant pathogenic fungi and change their colony morphology by inhibiting mycelial germination and changing the secondary metabolites. Furthermore, microscopic observation showed that the treatment of ethyl acetate extract could reduce the number of spores, shrink the mycelium, enhance the membrane permeability of pathogens, and therefore inhibiting their reproduction and growth progress. In conclusion, ethyl acetate extract of A. argyi powder has broad-spectrum antifungal activities, which has the great potential of developing botanical fungicides.