The invention discloses a dedusting device for the top of a cement storage tank. The dedusting device comprises a top cover, a positive-pressure air feeder, a spraying device and a drainage pipeline. The top cover is buckled to an opening in the top of the cement storage tank. The bottom of the top cover is welded to a tank body of the cement storage tank. The interior of the top cover is divided into a first space and a second space through a first vertical partition board. Air blowing area is formed in the first space and located at one side of the opening in the top. A spraying area is formed in the second space and located at the other side of the opening in the top. The positive-pressure air feeder is arranged in the first space, and the air feeding direction of the positive-pressure air feeder is from an air feeding port to the spraying area. The spraying device is arranged in the spraying area. The upper end of the drainage pipeline is communicated to the lower portion of the second space. The lower end of the drainage pipeline is communicated with a sedimentation basin. According to the dedusting device for the top of the cement storage tank, the situation that cement powder floats in air, and thus air is polluted can be prevented, cement paste is prevented from flowing out along the storage tank, cement paste sediment is avoided, and the cleaning workload is reduced.