The invention discloses a magnetic nanoparticle/SiO2 aerogel and a preparation method of the magnetic nanoparticle/SiO2 aerogel and a method for treating high level liquid waste by using the magnetic nanoparticle/SiO2 aerogel. The preparation method comprises the following steps: (1) preparing a nonionic surfactant to be mixed with a nitric acid aqueous solution, and then successively adding an organosilicone source and ethanol to obtain an SiO2 alcosol;(2) preparing an aqueous solution of metal nitrates, then adding glycollic acid to carry out complexation reaction, and heating and carrying out desolution after adjusting the pH value to obtain a spinel precursor gel; (3) mixing and stirring the prepared SiO2 alcosol and the spinel precursor gel till gelling, replacing a solvent by anhydrous ethanol after the gel is aged, and then drying and performing heat treatment to obtain the magnetic nanoparticle/SiO2 aerogel. The magnetic nanoparticle/SiO2 aerogel disclosed by the invention is an adsorption material with high specific surface area, high adsorption capacity and magnetism, and not only can separate and recycle an adsorbent, but also provides a new technical way for treating the high level liquid waste.