Abstract: Pyridazinone is a family of heterocycle with good biological activity.In order to find new insect growth regulators,benzoylphenylurea was introduced into 5-position of 3(2H)- pyridazinone ring based on the former research.Seventeen 5-benzoylphenylurea-3(2H)-pyridazinones were designed by linking sub-active group and synthesized in two methods.Their structures were confirmed by 1H NMR,IR and elemental analysis.In the preliminary bioassay test,some compounds such as 6a,BPU-4 showed good activity against the third-instar nymphs of locusts (Locusta migratoria manilensis Linne) (Meyen)at the concentration of 200mg/L.The title compounds,disrupting the growth and development of treated nymphs of locusts,exhibited obviously the effect as insect growth regulator (IGRs).