Abstract: In order to make high-valued use of the waste tea residue and broaden the plant fiber sources in wood-plastics composites, tea dust/polypropylene(TD/PP) composites were manufactured by open mill and injection molding process with TD as organic reinforcement and PP as matrix. Aiming to explore the outdoor application and weathering mechanism, the outdoor natural weathering form was applied and the effects of weathering time on the mechanical properties, color change and surface morphology of TD/PP composites were investigated. And the weathering mechanism was analyzed by FTIR. The results show that the contents of different extracts from TD is much higher but cellulose content in TD and ratio of fiber length to width is lower compared with wood fibers. The corresponding brightness difference, red green color index difference and yellow blue color index difference are 37.64, -10.40, -3.38 and 39.19, respectively after outdoor natural weathering for 8 months, and the bending strength, notched impact strength, flexural modulus and hardness of TD/PP composites are reduced by 38.7%, 42.4%, 41.4% and 9.14%, respectively. The photodegradation of PP matrices chain in TD/PP composites and lignin in TD are confirmed by FTIR analysis during the outdoor natural weathering process. And the SEM photograph indicates that there are obviously cracks on the surface of TD/PP composites, the quantity, depth and width of cracks increase, and there even occurs pulverization phenomena in some place.