Using the methods of high-speed mixing, screw extrusion, and injection molding, wood-plastic composites (CS-PF-ASFX) with inorganic fibers (aluminum silicate fibers, ASF) and organic agricultural wastes (cotton stalk, CS) as reinforcing fillers were prepared. The effects of different contents of ASF on the properties of wood-plastic composites were analyzed. Materials were characterized by Fourier infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG) analyses. The creep, relaxation, and mechanical behavior were also tested. With the increase of ASF contents, the FT-IR peaks at approximately 1740 cm-1 shifted to lower wavenumber, indicating the potential interactions between ASF and CS. The XRD patterns of the composites implied that the crystal structures of each component were maintained. Moreover, the addition of ASF enhanced the mechanical properties and thermal stabilities of CS-PF-ASFX composites, and the tensile strength and impact strength reached maximum of approximately 39.4 MPa and approximately 3.89 kJ/m2, respectively.