Abstract: Three kinds of elastomers, polyolefin elastomer (POE), elastomer modified polyethylene (BPB) and graft modified polyolefin elastomer (A669) were introduced to preparation process of wood flour/high density polyethylene (WF/HDPE) composite to improve the toughness of wood-plastic composites. The kinds and contents of toughening agent at which can simultaneously improve the toughness and maintain the rigidity of WF/HDPE composites were determined by the impact strength and flexural elastic modulus test of WF/HDPE composites. The toughening principles were analyzed by the aid of the crystallization behavior, thermal dynamic property and interface bonding analysis. Through comparison, it shows that A669 is the most effective one; when adding mass fraction is 4%, the impact strength is 15.31 kJ/m², increases by 52.34% comparing to the composite without A669, while the flexural elastic modulus just decreases by 6.09%. XRD and DSC analysis results show that, adding A669 hinders the crystallization behavior of WF/HDPE composites, which decreases the crystallization temperature and the crystallinity, while increases the grain size and the size of the diffraction surface corresponding to the diffraction angle. Thus more energy is absorbed and lost, and the glass transition temperature of WF/HDPE composite decreases. The DMA and SEM analysis results show that, the WF/HDPE composites with A669 present more viscosity characteristic, and the wiredrawing phenomenon of plastic matrix appears on the fracture surface, improving the toughness of the material. The torque rheometer test shows that, the balance torque of WF/HDPE composites does not change significantly, which indicates that A669 will not adversely affect the processing. Therefore, A669 can provide wood-plastic composite with both good toughness and stiffness under an appropriate use level. The results of present study will greatly promote the application of wood-plastic composite in building templates etc.