The rational design and precise synthesis of multifunctional hybrid nanostructures with a tailored active core and large, dendritic, modified mesoporous structured shell can promote catalysis, energy storage, and biological applications. Here, oil-water biphase stratification coating strategy has been developed for preparing monodisperse magnetic dendritic mesoporous silica core-shell structured nanospheres. These sophisticated Fe3O4@SiO2@dendritic-mSiO2 nanospheres feature large dendritic open pores (2.7 and 10.3 nm). Significantly, the silica shells can be converted to dendritic mesoporous aluminosilicate frameworks through a post-synthesis approach with unchanged porosity, considerable Si/Al molar ratio of 14.1, and notable strong acidic sites. Simultaneously, the resultant magnetic dendritic mesoporous aluminosilicate nanospheres emerge outstanding properties and promising application for phosphate removal in wastewater.