Abstract: The ethanol extracts from walnut green husk were further extracted with different solvents,including petroleum ether,chloroform,ethyl acetate and n-butanol. Antimicrobial activities of the different solvent extracts against 7 microorganisms were studied with the plate diluting method. The results showed that the different solvent extracts had certain inhibition effects on testing microbial and the order was ethyl acetate extract >chloroform extract>n-butanol extract>petroleum ether extract. The ethyl acetate extract had obvious antibacterial effect and broad-spectrum antibacterial activity. The inhabitation of ethyl acetate extract was the best when the concentration was 50 mg/m L. Diameter of the inhibited ring was 19.94 mm to Staphylococcus aureus and the MIC( Minimum inhibitory concentration) and MBC( Minimal bactericidal concentration) were 0. 781 and1.563 mg/m L respectively. Temperature and ultraviolet(uv) had no effect to antibacterial activity,Na Cl and sucrose had little influence on it,but it was greatly influenced by p H of culture medium and solution. The mainly antimicrobial mechanism was to destroy bacteria cell wall or membrane structure.