An uncertainty study for fiber permeability measurement is presented in this paper. The sources of uncertainty were identified. This paper focuses on the instrument and environmental uncertainties. The parameter uncertainties of both unsaturated and saturated measurements were estimated based on instrument accuracy limitations and environmental influences. Their influences on the permeability uncertainty were investigated by uncertainty propagation and Monte Carlo simulation. The significant factors affecting the permeability measurement uncertainty were identified. The results show that (1) unsaturated measurement has a higher accuracy than saturated measurement; (2) the significant factors affecting measurement results are pressure and viscosity. Based on the simulation results, the approaches to reduce measurement uncertainty were proposed.