A series of hierarchical flower-like magnesium oxide (MgO) microspheres were prepared with an ethylene glycol (EG)-assisted route at room temperature using ammonia as a precipitating agent. Effects of the ethylene glycol (EG) ratio on the structure, morphology and pore properties were carefully investigated. The hierarchical porous MgO microsphere exhibited a surface area of 75 m 2 g −1 and total pore area of 47.37 m 2 g −1 at the highest ratio of EG (EG/Mg 2+ = 10) in the reaction system. The prepared MgO microspheres exhibited an outstanding removal capacity of 574.71 mg g −1 for phosphate following the pseudo second order kinetic model ( R 2 = 0.99) and Langmuir isotherm model with the endothermic nature of phosphate adsorption which resulted from the high surface area and suitable pore size. Both the isothermal parameter R L between 0 and 1 and the negative the Gibbs free energy value suggested that phosphate adsorption on a MgO microsphere was a favorable process. Undoubtedly, this template-free mild synthesis method effectively promotes wide practical applications and mass scale production of porous MgO microsphere adsorption material. Hierarchical porous flower-like MgO microspheres were fabricated via an ethylene glycol-assisted route under mild conditions and exhibited an outstanding maximum adsorption capacity of 574.71 mg g −1 for phosphate.