The invention provides a radiation shielding composite material and a preparation method thereof. The preparation method comprises the steps of (1) mixing bisphenol A type epoxy resin and bisphenol F type epoxy resin, and heating in water bath; (2) mixing sodium phytate, nano samarium oxide, nano tungsten oxide, nano gadolinium oxide and multiwalled carbon nanotube, and performing ball-milling; (3) adding butyl stearate, liquid paraffin and acetone, and performing ultrasonic dispersion; (4) adding silane coupling agent Si-602, vinyltriethoxysilane and vinyl tris (beta methoxyethoxy) silane, and continuously performing ultrasonic dispersion; (5) adding resin in step (1) into a mixture in step 4, and stirring; (6) cooling to normal temperature, adding trimellitic anhydride and methyl tetrahydrophthalic anhydride, and stirring; (7) pouring a new mixture into a mould, putting into a vacuum drying chamber and curing, thereby obtaining the radiation shielding composite material. The radiation shielding composite material provided by the invention has good mechanical property, has excellent radiation shielding performance at the same time, and has very good protecting effect on radiation.