Provided is a method for preparing a drug loaded nanoparticle comprising: dissolving a macromonomer, a stabilizer and a crosslinker in a solvent to create a mixture； adding an initiator system to the mixture； dissolving a drug or combination of drugs in an organic phase containing the mixture； and recovering the drug loaded nanoparticle, a composition comprising the drug loaded nanoparticle prepared by the above method, and a method for treating cancer comprising administering the above composition to a subject in need thereof.
