The invention discloses a preparation method for multilayer gradient porous polypropylene beads. The preparation method comprises the following steps: (1) respectively adding different bubble nucleating agents into three or more polypropylene raw materials with different melting points, mixing through an extruding machine, performing multilayer co-extruding, drawing, and cutting particles to obtain polypropylene micro-particles; (2) throwing the polypropylene micro-particles into a reaction kettle, heating and pressurizing, so that the polypropylene micro-particles absorb a large amount of gas at a high temperature and high pressure; (3) when the temperature is at the melting point of the polypropylene micro-particles, opening a deflation valve of the reaction kettle to relieve the pressure to atmospheric pressure to obtain the multilayer gradient porous polypropylene beads of which the surfaces are clinkered and the internal hole diameters change in a gradient manner. The preparation method for the multilayer gradient porous polypropylene beads disclosed by the invention is simple in process and convenient to operate, and has low requirement on equipment; multilayer gradient bubble hole distribution is easy to control, and industrialization is easy to realize. Each layer in the beads has a plurality of complicated functions, and the cost can be effectively reduced. The multifunctional polypropylene beads are widely applied in the fields, such as automobiles, food and medical equipment.