The invention discloses a method for preparing magnetic cellulose aerogel by utilizing waste paper. An ultra-light multi-porous gas magnetic hydrophobic aerogel adsorbing material is prepared by using waste paper fibres in life as a raw material; waste paper regenerated cellulose gel is prepared by utilizing an microwave auxiliary ionic liquid dissolution method; black red waste paper cellulose aerogel is obtained through magnetic modification and hydrophobic and oleophobic modification. The magnetic cellulose aerogel disclosed by the invention can effectively remove a variety of organic pollutants and oily materials leaked in water; the absorption multiplying power is high; oil is absorbed thoroughly; an adsorbing material is non-toxic and harmless; the adopted magnetic collecting method is simple and easy to use; secondary pollution is low; the preparation method is simple in process and mild in conditions; waste can be changed into treasure by conventional industrial equipment and low-cost raw materials; the emission of waste water, waste gas and waste residues is avoided in a production process; the method has a wide popularization application value and social significance.