Aiming at the problems that the oil-recovery-efficiency of oilfield in very high water-cut stage is low and polymer water invasion resistance agents reduce the early hydration rate of cement paste and cementing quality of high-pressure water-cut stratum, this study was carried out to prepare nanofiber as a new type of water invasion resistance agent using plant cellulose fibers combining wet ultrafine ball milling and 2,2,6,6-tetramethylpiperidine oxide (TEMPO) oxidation methods. The effect of nanofiber on the rheological properties, consistency time, compressive strength and water invasion resistance of cement paste was investigated. The results show that the nanofiber have the effects of increasing viscosity and promoting early hydration of cement paste. When the mass fraction of nanofiber increases to 0.2%, the liquidity index of cement paste decreases from 0.849 to 0.557, the yield stress increases from 2.305 Pa to 10.061 Pa, the consistency time slightly reduces from 260 min to 219 min, and the 14 d compressive strength improves from 26.8 MPa to 41.0 MPa. The nanofiber could enhance the cohesion of cement paste by bridging and adsorption, and increase the hydration rate and early compressive strength of cement by changing nucleation site, which is beneficial for improving the bonding quality between cement stone and stratum rocks and cementing quality.