Abstract: The structure characteristics of neonicotinoids insecticides imidacloprid (IMI) and thiamethoxam (TMX) and the research progresses on the metabolisms of IMI and TMX in mammals,plants and insects,especially the metabolic pathway and the relative major enzymes in the metabolism of IMI and TMX are reviewed.IMI and TMX could be gradually metabolized by mammals,plants,microorganisms and insects in the environment.Microsomal cytochrome 450s(CYP450s) and cytosolic aldehyde oxidase (AOX) are the major enzymes involved in the metabolism of IMI and TMX.CYP450s isozymes are responsible for the hydroxylation,desaturation,dealkylation and nitro reduction of imidacloprid and thiamethoxam,while AOX reduced the nitro group of IMI and TMX.The biological activities of some metabolites of IMI and TMX are usually lower than that of native IMI and TMX,but in some cases,IMI and TMX act as proinsecticides,which could be metabolized to more potent nicotinic agonists.The activated metabolites of IMI and TMX would improve the insecticidal activity against the pest insects and the risks for non-target organisms.Identification of the metabolic pathway,metabolites and activities of neonicotinoids are important for understanding the toxicity mechanism of neonicotinoids metabolism,as well as the safe and efficient application neonicotinoids insecticides.