AbstractPyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to investigate the primary pyrolysis product distribution of the pyrolysis of wood-plastic composites (WPCs) and the mutual effects of poplar wood (PW) and high-density polyethylene (HDPE). The PW, HDPE, and WPCs were pyrolysed at 475, 550, and 625 °C. The effect of temperature on the WPC pyrolysis products was examined. The comparison of the degradation composition results for HDPE, PW, and WPCs indicated that thermal degradation of WPCs comprised individual poplar wood and HDPE pyrolytic decompositions, and the pyrolytic products of PW and HDPE did not react with each other. The experimental results demonstrate that the pyrolytic product distribution of HDPE changed apparently in the presence of PW during pyrolysis. The PW decomposed at lower temperature during pyrolysis provided radicals, enhancing the scission of polymer chains to obtain more light paraffins. Further, the proposed pathway for the evolution of the main volatile organic products was probed. This study provides insights into the fundamental mechanisms of WPC pyrolysis and a basis for developing more descriptive models of WPC pyrolysis.