The invention relates to a plant fiber particle-filling regeneration polyester composite material and a preparation method thereof. The plant fiber particle-filling regeneration polyester composite material is prepared by, by weight, 50-80% of regeneration polyester, 10-20% of polyolefin, 5-30% of plant fiber particles, 2-10% of compatilizer, 2-8% of chain extender, 0.2-1% of antioxygen and 0.2-2% of lubricating agents. The raw materials are fused and then particles are squeezed out and the plant fiber particle-filling regeneration polyester composite material is obtained. According to the plant fiber particle-filling regeneration polyester composite material and the preparation method thereof, the performances (tenacity, transparency and the like) are excellent, sources for raw materials are wide, cost is low, recycling and reusing are available, environment pollution is reduced, and resources are saved. Compared with various inorganic and synthetic fibers, the plant fiber particles have the advantages of being low in price, easy to obtain, low in density, high in tensile strength and modulus, and small in energy consumption for processing, renewable and compatible with the ecological environment, small in environment pollution, small in damage to human bodies, and capable of meeting requirements of the ecological environment, large in economic potential, and applicable to the fields such as automobile industries, interior decoration, and electric products.