Abstract: Hemp fiber/polypropylene(HF/PP) composites were prepared via non-woven and compressing technology. The volatile organic compounds(VOC) emission source of HF/PP composites was studied and TG-mass spectrometry (TG-MS) was used to study the effect of PVA and urea modification on the VOC emission of HF/PP composites. At the same time the effect of the above methods on the mechanical and thermal properties of HF/PP composites were also investigated. The results reveal that the VOC emission of HF/PP composites mainly comes from hemp fiber. Compared with the untreated composite, the mechanical properties of the modified HF/PP composites are improved. The tensile strength and flexural strength of the composite reach the maximum value after urea modification which increase by 19.32% and 15.04% compared with untreated. The tensile modulus, flexural modulus and impact strength of the HF/PP composite reach the maximum value after PVA modification which increase by 17.72%, 15.94% and 24.72% compared with untreated. The thermal stability and VOC emission of the modified HF/PP composites are optimized after modification. The HF/PP composite attains the optimal thermal stability after PVA modification, and the total activation energy increases by 121.99% compared with untreated, and reaches to 392.56 kJ·mol^-1. The thermal stability of HF/PP composites is closely related to its interfacial properties. The total VOC cumulative emission of the modified HF/PP composites decreases compared with untreated, and the urea modified composite exhibits the best effect.