The invention discloses an amphiphilic superparamagnetism magnetic resonance contrast medium and a preparation method thereof. The contrast medium takes MnFe2O4 nanometer grains as cores; polyalcohol molecules evenly clad the surfaces of the MnFe2O4 nanometer grains; and part of hydroxies on the outer ends of the polyalcohol molecules react with 9-fluorenylmethyl chloroformate to form amphiphilic shell structures through acyl chloride reactions. The preparation method comprises the following steps: taking the polyalcohol as a solvent, pyrolyzing ferric and manganese acetylacetonates at a high temperature to obtain the MnFe2O4 nanometer grains clad by the polyalcohol molecules through, and then carrying out the acyl chloride reaction between 9-fluorenylmethyl chloroformate and polyalcohol hydroxies on the surfaces of the nanometer grains. The contrast medium has the advantages of small grain size, high crystallinity, high saturation magnetization rate, high relaxation capability, good biological compatibility, low toxicity and good stability. The preparation method has the advantages of simple operation, low cost, low requirements on the equipment, and easy realization of industrialized production.