Three kinds of modified poplar wood fibers(PWF) named hexadecyltrimethoxysilane(HDS) impregnated modified poplar fiber(HPWF), 1H, 1H, 2H, 2H-perfluorodecyltrimethoxysilane(FDS) impregnated modified poplar fiber(FPWF1) and FDS spray modified poplar fiber(FPWF2) were obtained by respectively using HDS and FDS as modifiers and ethanol-water solution as dispersing media by impregnation and spray methods. The effects of solvent ratios, dosage of silanes, hydrolysis temperature and time of silanes, reaction temperature and time on the surface modification of PWF were studied. The chemical structures and surface properties of unmodified and modified PWF were investigated by Fourier transform infrared(FT-IR) spectroscopy, contact angle measurement, X-ray diffraction(XRD), X-ray energy dispersive spectrometer(EDS) and scanning electron microscope(SEM). HPWF was treated with HDS(hydrolyzed at 60℃ for 1 h) at 60℃ for 1 h in ethanol/water solution. The results showed that when the molar ratio of HDS to active hydroxyl of PWF was 0.4:1 with ethanol mass fraction of 60%, the surface contact angle of HPWF was up to 139°; when the molar ratio of FDS to active hydroxyl of PWF was 0.16:1 with ethanol mass fraction of 50%, the surface contact angle of FPWF1 was up to 141°. Specially, the surface contact angle of FPWF2 was up to 138° when the fiber was wetted at the molar ratio of FDS to active hydroxyl of PWF 0.008:1, and then activated at 120℃ for 1.5 h. Compared with the impregnation method, the spray method had the advantages of small dosage of silane, simple process, cleanliness and high efficiency. In addition, the modified fibers had the properties of higher crystallinity(from 62.1% to 67.7%-69.7%), rougher surface, bigger specific surface area, lower surface polarity, and higher hydrophobicity, which were conducive to improving the interfacial compatibility and bonding with hydrophobic resin matrix.