Abstract: The co-pyrolytic behaviors of pine sawdust and low-density polyethylene(LDPE) were investigated by TG and DSC methods. The yield and composition of the pyrolyitc products from different ratio of the pine sawdust to LDPE mixtures were studied by heating with microwave. The results showed that pine sawdust and LDPE can be co-pyrolyzed in the range of 270-480℃, which can be divided into two sections before and after 375℃. It was observed that the co-pyrolytic effect took place at the weight ratio of co-pyrolytic pine sawdust to LDPE below 10:2. The gas chromatography-mass spectrometry (GC-MS) analysis results showed that the yield of co-pyrolytic liquid, especially guaiacols generated from wood, was reduced with the amount of LDPE increasing and microwave power enhancing. However, 1-hydroxy-2-propanone and acetic acid were increased considerably, which exceeded half content of the liquid products. The higher microwave power was used, the more non-condensable gases were generated. It was also found that the increasing amount of LDPE boosted the generation of oxycarbide gases.