Xanthoceras sorbifolia is one of the most important oil plants and also has great officinal and ornamental value.It is mainly grown in northern part of China.The seeds can be used to produce plant oil.However,the abundant fruit husks are left as wastes.How to make these waste materials useful becomes challenging.Since the husks are rich of celluloses,it might be a solution to incorporate the husks into polymer to develop natural fibers polymer composites.Before compounding into PP or PE,the husks were alkali treated to remove waxes and other noncellulosic components,bleached to change its color and diminish its dimension,and surface modified with different coupling agents to decrease its polarity,etc.As for PP composites,fibers with alkali-KH570 treated have the best mechanical performance except the alkali-bleach treated one.With regard to PE composites,different processing methods were adopted.The composites with twice compounding by twin screw extruder perform better than once.Subsequently the effects of different fiber contents on the mechanical properties of PP and PE composites were investigated,and the results show a decreasing trend with the increase of the fiber content in general.Scanning electron microscopy (SEM),Fourier transform infrared spectroscopy (FT-IR),thermo gravimetric analysis (TGA),tensile and impact tests were employed for the fibers and composites.These natural fibers filled polymer composites show good mechanical properties and have potential applications in automobile,construction and packaging industry.