Abstract: In order to investigate the influence of antimildew agent zinc borate on the fungus corrosion resistance of wheat straw/polypropylene (PP) composites, the fungus accelerating corrosion experiments of wheat straw/PP composites with different contents of zinc borate were conducted. The mechanical properties, color variation and water absorption of composites after corrosion were tested. And FTIR was used to analysis the changes of functional groups of composites. Also the surface mildew growth and microstructure of composites were observed by stereomicroscope. The results show that the zinc borate could improve the corrosion resistance of wheat straw/PP composites. The optimum additive amount of zinc borate is 2wt%, wheat straw/PP composites have little mildew on the surface and flexural strength, flexural elastic modulus, tensile strength and impact strength are increased by 6.5%, 50.2%, 6.8% and 11.1% respectively after corrosion compared with non-adding zinc borate composites. The water absorption rate and color difference value are decreased by 23.9% and 30.7%. The zinc borate could effectively prevent the mildew corrosion to the cellulose and hemicellulose of wheat straw in wheat straw/PP composites when the content of zinc borate is 2wt% and interface wheat straw fiber is easily corrodible by fungus when the content of zinc borate is more than 2wt% due to its effect on interface of composites.