In order to search for new insect growth regulators, fifteen new compounds containing 5-oxo- 3(2H)-pyridazinone derivatives were designed and synthesized. Their structures were confirmed by ¹H NMR, IR Spectra and elemental analysis. In the preliminary bioassay test, compound 8o obviously disrupted the development of second-instar housefly larvae. Compounds 8a, 8c, 8g and 8j also showed good activity against the third-instar nymphs of locusts (Locusta migratoria manilensis). The structure-activity relationship of compounds was also discussed.