On the excellent optical performance of grapheme, a graphene-based all-fiber electro-absorption modulator was constructed. The structure of the modulator was designed, and simulation and experiments for the modulator were both conducted. Firstly, the relationship between the chemical potential and the permittivity was researched according to the graphenes optical properties, then the graphene-based all-fiber modulator was designed, and the dependence of the effective refractivity of the modulator on the chemical potential was analyzed. The proposed graphene-based all-fiber electro-absorption modulator was simulated and was compared to traditional semiconductor modulators. Finally, the graphene-based all-fiber electro-absorption modulator was developed and its performance was tested. The simulation results show that the modulation efficiency of the quadri-layer all-fiber graphene modulator reaches up to 0.233 dB/mm, and the footprint has been reduced to only 12.9 mm with the swing voltage lower than 0.2 V. The experiments demonstrate that the proposed modulator is feasibility. Limited by the practical conditions, the tested half-wave voltage is about 120 V and the 3 dB bandwidth is around 100 MHz. As compared with traditional graphene-based waveguide modulator, the proposed modulator shows a smaller half-wave voltage, higher modulation efficiency, and a smaller size. Moreover, it has a lower insert loss and is suitable for all-fiber systems in future.