The invention relates to a method for preparing a neonicotine pesticide clothianidin and belongs to the technical field of a pesticide. The method comprises the following steps of: 1, synthetizing an intermediate 1,5-dimethyl-2-nitryl imido-hexahydro-1,3,5-triazine; 2, synthetizing an intermediate 1-(2-chloro thiazole-5-methyl-2-nitryl imido-3,5-dimethyl-hexahydro-1,3,5-triazine (which is called as TST for short); and 3, synthetizing the clothianidin. In the method for preparing the neonicotine pesticide clothianidin, which is disclosed by the invention, the clothianidin is generated by decomposing 1-(2-chloro thiazole-5-methyl-2-nitryl imido-3,5-dimethyl-hexahydro-1,3,5-triazine, and the clothianidin with purity content of higher than or equal to 95 percent can be prepared. The method has the advantages of high selectivity, mild reaction condition, short reaction time, high product purity and easiness in realizing industrialization.