The invention relates to a sustained-release granular formulation for preventing and treating 
crop diseases and 
insect pests and a preparation method thereof. The 
pesticide sustained-release granular formulation comprises 
bentonite, an organic modifier, 
pesticide active ingredients, an 
inert filler and a binding agent, and is prepared by the preparation method comprising the steps of: (1) with the 
bentonite as a basic material, modifying the 
bentonite by the organic modifier to obtain organic bentonite; (2) loading the 
pesticide active ingredients on the organic bentonite to prepare 
medicine-carrying organic bentonite; and (3) mixing the 
medicine-carrying organic bentonite, the 
inert filler and the binding agent proportionally, and pelleting to obtain the sustained-release granular formulation. The preparation method of the sustained-release granular formulation, provided by the invention, not only overcomes the defect of low pesticide 
loading rate of the natural bentonite, but also realizes the 
controlled release of the pesticide by adjusting a 
chemical structure and the amount of the modifier, so that the sustained-release granular formulation is coincident with an occurrence rule of the 
plant diseases and 
insect pests, and the pesticide sustained-release granular formulation is used safely, reasonably, economically and effectively.