The invention provides a multifunctional opening foaming polymer particle and a preparation method thereof. The method includes the steps that nano-titanium dioxide or nano-zinc oxide or nano silver powder or nano zinc sulfide is used as a multifunctional auxiliary, an appropriate coupling agent, polymeric dispersant, antioxygen and polymer resin are further adopted, a twin-screw extruder is used for achieving melt blending to conduct extrusion and particle cutting, functional nano powder is wrapped in matrix resin so that polymer particles can be formed, then the polymer particles are foamed by supercritical carbon dioxide gas, the multifunctional opening foaming polymer particle with excellent performance can be prepared, the particle has a surface opening through hole structure and an inner continuous large hole structure, the particle size is 0.5-5 mm, and the opening hole diameter and the inner through hole diameter of the surface of a particle spherical shell both can reach 50 nm-10 microns. The preparation method is simple in technology, convenient and easy to implement. The prepared opening foaming polymer particle has the functions of absorption, filtering, antibacteria and mold prevention, catalysis, odor removal, formaldehyde removal, anti-ultraviolet ageing and the like.