We proposed and studied an all-optical modulator based on graphene-microfiber (GMF), and prepared GMF by transferring graphene to the surface of the tapered region of the microfiber. The all-optical modulation characteristics and ultrafast all-optical modulation characteristics of GMF under different light source combinations were studied, and the all-optical modulator was completed. The experimental results show that GMF can achieve all-optical modulation, and broadband pump light can modulate single-pulse signal light. When the pump light is a 1550 nm ASE light source, and the signal light is a single-pulse light source of 852 nm, the maximum modulation depth is 3.92 dB. A single-pulse pump light can modulate single-pulse signal light. When the pump light is a 980 nm single-pulse laser, and the signal light is a 1550 nm single-pulse laser, the maximum modulation depth is 2.966 dB. The all-optical modulator proposed in this paper has ultrafast all-optical modulation characteristics. When using a femtosecond pulse laser as pump light, the average response time of the all-optical modulator is 51.43 μs, and the average equivalent modulation rate is 19.44 kHz. The all-optical modulator based on the GMF we proposed provides a new, to the best of our knowledge, idea for the design of graphene-based all-optical devices and shows great application potential in ultrafast all-optical networks.