Abstract: Abstract: The wood-plastic foamed composites have lower density and higher specific strengths than wood-plastic composites (WPC) and thus have wide applications in fields such as building, decoration, packing, and the automobile industry. Previous studies showed that the weathering causes color fading, strength weakening, chemical changes of WPC, thereby restricting the specific outdoor applications of WPC. In order to explore their weathering mechanism and broaden their outdoor applications, it is of great importance to evaluate the durability of BF/PP foamed composites. The objective of this research was to study the impact of weathering of freeze-thaw cycle on the physical and thermal properties of bamboo flour-polypropylene foamed composite. The foamed composites of bamboo flour (BF), high melted strength polypropylene (HMSPP), polypropylene (PP), 1% modified azodicarbonamide (AC) foaming agent, and maleic anhydride grafted polypropylene (MAPP) coupling agent blends were prepared by injection molding. The composites with different BF contents of 0, 20%, 33% and 42% were exposed to accelerated cycling of water immersion followed by freeze thaw at the temperature of -40?60℃ for 0, 3, 6, and 9 cycles. The effects of freeze-thaw cycles accelerated weathering on the color change and the physico-mechanical properties and thermal behavior of the foamed composites were investigated. The surfaces morphology of composites non-weathered and freeze-thaw cycles weathered were investigated by (Environmental Scanning Electronic Microscopy, ESEM) and the chemical structures were also analyzed by FTIR. The results showed that the composites at higher BF content exhibited greater color change and larger decreases in physico-mechanical properties especially the tensile and impact strengths as compared to the one without weathering. The negative effects of the weathering increased with the growing number of freeze-thaw cycles. The color change ΔE* of 0, 20%, 33%, and 42% BF/PP composites after nine times freeze-thaw cycles were 0.9, 2.4, 7.0, and 9.9, respectively. The corresponding lightness change ΔL*, redness change Δa*, and yellowness change Δb* of 42% BF/PP composite were 8.7, 1.3, and 4.7, respectively. The retentions of flexural modulus, and bending, tensile, and notched impact strengths of 0%, 20%, 33%, and 42% BF/PP composites were 95.2% - 99.1%, 97.3% - 98.9%, 94.9% - 97.5%, and 92.0% - 95.6%, respectively. The freeze-thaw cycles slightly affected the thermal behavior of composites as the initial temperature of thermal decomposition (Ti) for the 0% and 33% BF/PP foamed composite after nine times freeze-thaw cycles reduced by 19℃ and 8℃, respectively. ESEM observation revealed that the surfaces of freeze-thaw cycles weathered composites were no longer smooth; and the micro cracks and folds appeared; meanwhile, some parts of the polymers layers dropped off. FTIR analysis indicated that the wood index (the ratio of the peak intensity at 2 912 cm-1 and the peak intensity at 1 023 cm-1) reduced and the bamboo particles of the composites surfaces lost and the intensity of the groups for PP decreased due to the freeze-thaw cycles weathering.