A series of novel 2-(benzo [d] thiazol-2-yl)-1-(3-methyl-5-substituted-phenyl-4, 5- dihydropyrazol-1-yl) ethanone derivatives were synthesized and characterized by NMR, ESI- MS. Biological activity tests results show that compounds 4a, 4b, 4d and 4g displayed activity with MIC of 1.562 μg/mL against B. subtilis ATCC 6633, compound 4d displayed significant activity with MIC of 1.562 μg/mL against S. aureus ATCC 6538. Compound 4a ...