The invention discloses a blast hole insulating device and a blasting method. The blast hole insulating device comprises an insulating barrel, a first sealing cap, a second sealing cap and a cushion column, wherein the cushion column is made from a ceramic fiber or glass fiber material, the insulating barrel is provided with an insulating chamber for arranging an explosive material, the first sealing cap and the second sealing cap are respectively connected to two ends of the insulating barrel for sealing an insulating chamber, a side wall of the insulating barrel comprises a force-bearing layer, a water absorbing layer and a resistance reducing layer, the force-bearing layer, the water absorbing layer and the resistance reducing layer are distributed in turn from inside to outside, the cushion column is shaped like a hollow barrel, one end of the cushion column is sealed, the other end of the same is open, and the end, provided with an opening, of the cushion column is matched with the end, provided with the second sealing cap, of the insulating barrel in a contact manner when the insulating barrel is matched with the cushion column. The blast hole insulating device disclosed by the invention has the advantages of low cost and reduced working strength of a worker, and the influence of a water source on blast is avoided.