Rare earth is widely used as a ray shielding material due to its special electron layer structure, and Monte Carlo simulations are also widely used in ray shielding. Therefore, in this paper, based on the Monte Carlo simulation algorithm and FLUKA program, three kinds of rare earth, Gd2O3, Nd2O3, and La2O3, were selected as shielding fillers to prepare rare earth/polypropylene composite materials, and their shielding effect on X-ray at 120KV tube voltage was simulated. It is found that the three rare earths as shielding fillers have a shielding effect on X-ray under 120KV tube voltage, and Gd2O3 has the best effect on X-ray attenuation. When the thickness of the material is 0.06 cm, the shielding rate of pure Gd2O3 particles is 92.25%, and the rare earth/polypropylene composite material with a mass ratio of 1: 1 at the same thickness can also shield 32.74% of rays. Increasing the thickness of the composite or the amount of rare earth filling can improve the shielding effect of the composite, but the effect of increasing the amount of rare earth filling is more significant.