Synthesis of pyrazole derivative using microwave energy has been carried out. The compound 1-[4-(2-hydroxy-ethoxy)-phenyl]-ethanone, is prepared from p-hydroxy-acetophenone and 2-chloro-ethanol. Chalcone derivative has been prepared by the condensation reaction of 1-[4-(2-hydroxy-ethoxy)-phenyl]- ethanone with 4-chlorobenzaldehyde. This chalcone. derivative cyclised with hydrazine hydrate and glacial acetic acid under microwave irradiation conditions give pyrazole derivative. These products have been characterized by detailed spectral analysis and have been screened for their antimicrobial activity, against Escherichia coli, Proteus vulgaris, and Salmonella typhimurium.