In order to investigate the inhibition effect of Artemisia argyi powder (a byproduct of A. argyi var. argyi ‘Qiai’ made of moxa) on plant pathogenic fungi and the potential to develop botanical fungicides,A. argyi powder were extracted by water,50% ethanol,ethanol,ethyl acetate and petroleum ether,and the fingerprints of different solvent extracts were established to compare the differences. Meanwhile,the antifungal activity of different extracts was tested to screen the strongest antifungal active parts in the A. argyi powder. In addition,the virulence equation and EC50 value of the ethyl acetate extract against nine kinds of plant pathogenic fungi were determined by the 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 than nonpolar solvents (petroleum ether),and there were great differences in the properties and components among the five solvent extracts. Among them,the fingerprints of pure ethanol extract and ethyl acetate extract were similar,and the main components were kaempferol,jaceosidin,eupatilin and other flavonoids. The antifungal activities of the 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 the 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 inhibit their reproduction and growth progress. In conclusion,ethyl acetate extract of A. argyi powder has broadspectrum antifungal activities,which has great potential of developing botanical fungicides.