Abstract: aryl-1,4-dihydro-3-acylhydrazinocarbonyl-6-methylpyridazin-4-one(4) was synthesized by two methods. The better process was chosen to prepare a series of the target compound in order to find novel bio-active co mpounds. Their structures were confirmed by IR, 1H NMR and elemental a nalysis. The preliminary bioassay showed that the title compounds pos sess promoting cucumber cotyledon root-formation activity. Some of the compound s exhibit antiviral activity against TMV and Sheath blight on rice.