The invention belongs to the technical field of preparation of inorganic materials and relates to flower-ball-like LDHs (laminar double-metal hydroxides), a preparation method and an application. Firstly, LDH slices are prepared through a T-type r Y-type microchannel reactor, the LDH slices and a surfactant are subjected to a reaction, finally, the reacted LDH slices are subjected to surface modification through spray drying, and LDHs are modified to form flower-ball-like LDHs formed by the LDH slices and having a hydrophobic property. A preparation process is simple, the repeatability is good, the cost is low, the production is environment-friendly, and the market prospect is broad; besides, by means of the unique flower-ball-like structure, flower-ball-like LDHs have an excellent hydrophobic property, and the waterproofness of a coating can be improved particularly after flower-ball-like LDHs are added to the coating.