Using Chinese white poplar flours(WF) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P34HB) as raw materials, the P34HB/wood flour bio-composite was prepared by hot pressing method. The changes of structure, mechanical property and thermal stability of the composite during natural degradation were studied by scanning electron microscopy(SEM), differential scanning calorimetry(DSC), thermal gravimetric(TG) analysis and mechanical property analysis. The results showed that the earlier stage of degradation was mainly the degradation of P34HB matrix, and the degradation of wood fiber was followed; the P34HB matrix presented honeycomb structures after degradation. The mass loss of the composite showed a near-linear upward trend with the time increasing, and the ratio of mass loss of the composite reached 34.43% after 100 days degradation. TG and DSC results further showed that the main degradation material of the composite was P34HB matrix, and the degradation of wood flour fiber was accompanied in the later stage. The flexural strength and Young's modulus of the composite decreased with the degradation time increasing, and the decrease trends were rapidly in first 10 days, which were from 24.67 and 2 768.25 MPa to 16.72 and 1 339.34 MPa, respectively, and the decrease rates were 32.23% and 51.62%, respectively. After 80 days of degradation, the flexural strength and Young's modulus of the composites reached 6.74 and 469.43 MPa, which decreased by 72.68% and 83.04%, respectively, and then they tended to balance.
