The utility model discloses a smoke pre-desulfurization system comprising a pre-spraying device and a pre-circulating pump. An inlet of the pre-circulating pump is communicated with a lime stone slurry pond, and an outlet of the pre-circulating pump is communicated with the pre-spraying device which is arranged in an inlet flue of a desulfurization absorption tower. In the system, the pre-desulfurization system is additionally arranged at an inlet of the desulfurization absorption tower, slurry in the lime stone slurry pond is fed into the inlet flue of the desulfurization absorption tower, so as to enable smoke to be subjected to primary pre-desulfurization before entering the desulfurization absorption tower, thus improving the desulfurization efficiency of a desulfurization device, and solving the problem that the desulfurization efficiency is low caused by practical coal types; and compared with the reconstruction method that a desulfurization tower body is modified, a spraying layer is additionally arranged on the tower body, and the like, the smoke pre-desulfurization system has the advantages that the change is small, and the reconstruction and installation cost is low.