Abstract: In response to the common problems of poor strength, toughness, stability, and limited application fields in traditional wood plastic composites (WPCs), micro-nanofiber (MNF) / high-density polyethylene (HDPE) modified pellets were prepared by extrusion and granulation through a wet feeding method. A novel wood plastic composite material was successfully prepared by combining MNF/HDPE modified pellets with poplar powder and additives. Electron microscopy observation exhibits that compared with the "island structure" formed by wood powder and plastic in the traditional wood plastic composites, the MNF in the novel wood-plastic composite can form a three-dimensional network interlocking structure with the HDPE matrix. MNF and wood flour play a synergistic role. Compared with the traditional wood-plastic composite, the novel wood-plastic composite shows an improvement of more than 56.5% in flexural strength and 63% in tensile strength. The novel wood-plastic composite has a linear thermal expansion coefficient as low as 37×10⁻⁶/K in the temperature range of −30°C to 60°C, and its water absorption rate is approximately 2% within 24 hours. In addition, the dynamic mechanical properties and creep resistance of the novel wood-plastic composites have also been significantly improved.