The invention relates to a tea leaf-polyolefin composite material which is prepared from the following raw materials in percentage by weight: 30-35% of tea leaf fine powder treated by a silane coupling agent, 52-58% of polyethylene, 6-10% of maleic anhydride grafted polyethylene, 0.5-0.8% of stearic acid, 1-2% of PE (Poly Ethylene) wax and 0.5-0.8% of antioxidant. The preparation method comprises the following steps: S1, obtaining the tea leaf fine powder treated by the silane coupling agent; S2, preparing treated tea leaf fine powder, polyethylene, maleic anhydride grafted polyethylene, stearic acid, PE wax and antioxidant; S3, adding the treated tea leaf fine powder into a high-speed mixer; S4, adding the maleic anhydride grafted polyethylene; S5, adding polyethylene into the high-speed mixer; S6, adding the stearic acid, PE wax and antioxidant; and S7, obtaining the tea leaf-polyolefin composite material. The material provided by the invention has the beneficial effects that the performance requirements of functional biomass high polymer materials are satisfied; the composite material is a low-cost and green high polymer material which not only has the characteristic of conventional polyethylene, but also is degradable and can be used for improving the mechanical properties of plastic products.