The invention provides graphene oxide-diatomite composite adsorption microspheres with three-dimensional porous structures and a preparation method. High-dispersity graphite oxide and diatomite with a porous structure serve as main raw materials, graphene oxide and sodium alginate serve as composite film forming matters, and an internal three-dimensional porous structure is finally achieved by using an expansive action generated by flash evaporation of water molecules, a template effect of inorganic particle diatomite, a van der Waals force among graphene oxide and a nano fiber reinforcement effect under microwave process conditions. According to the composite adsorption microspheres with the three-dimensional porous structures, the adsorption performance of the material is improved by making full use of high specific surface area of the graphene oxide, the porous structural characteristic of the diatomite, a large amount of electronegative functional groups such as cyclic amino, hydroxyl and carboxyl attached to a six-membered ring of the graphene oxide and different types of hydroxyl groups attached to the surface of the diatomite. Meanwhile, the comprehensive adsorption performance of the material is further improved by dint of the three-dimensional porous structure formed under the microwave process conditions. The problems of graphene adsorption materials that the preparation process is relatively complicated, the cost is high, and the application is difficult are solved.