The invention relates to a vortex-induced vibration suppression device and method for discharging and sucking seawater by pressure difference of fluctuation of waves. The vortex-induced vibration suppression device is composed of a bracket and a seawater sucking system. The bracket is used for fixing the seawater sucking system on a marine riser. The seawater sucking system is composed of eight auxiliary circular pipes evenly distributed in the circumferential direction of the marine riser. Seawater discharging and sucking holes distributed in a staggered mode are formed in the upper parts ofthe auxiliary circular pipes, gas chambers are formed in the lower parts of the auxiliary circular pipes, the chambers are filled with compressible gas, disc-shaped pistons and limit rings are sequentially arranged on the upper part of the chambers, and the pistons can freely move up and down in the lower spaces of the limit rings. The vortex-induced vibration suppression device utilizes the pressure difference of the fluctuation of the waves to induce seawater to be continuously sucked and discharged from the auxiliary circular pipes, the boundary layer separation and vortex shedding of the marine riser are disturbed under the combined actions of the constant adjustment of the flow and momentum and the interference of a flow field of the auxiliary circular pipes, and thus the vortex-induced vibration suppression is realized without energy consumption.