In the present study a series of 3-(2-Hydroxy-3, 5-dichlorophenyl)-5-(4-chloro phenyl) isoxazole (8a) and 3-(2-Hydroxy-3, 5-dichlorophenyl)-5-(2, 4-chloro phenyl) isoxazole (8b) have been synthesized by refluxing the chalconedibromide (6a) and (6b) with hydroxyl amine hydrochloride in ethanol containing catalytic amount of piperidine. The formation of the above synthesized compounds was confirmed on the basis of their chemical tests and spectral analysis. The synthesized heterocycles then screen for their antimicrobial activity against some kahrip plant pathogens viz. AlternariaMacrospor, XanthomonasCampestris, Pseudomonas syringae and Fusarium Spp. From the above study the result revealed that isoxazole derivatives shows good to moderate antimicrobial activity against plantpathoges.