The utility model provides a downpipe with the heat preservation function for a building and belongs to downpipes outside a building body. The downpipe comprises a downpipe body. A heat preservation layer made of a polystyrene material is arranged at the outer layer of the downpipe body. A heat absorbing layer made of a black waterproof material is arranged outside the heat preservation layer. Ribs in the horizontal direction are arranged inside the downpipe body. According to the downpipe with the heat preservation function for the building, due to the fact that the heat preservation layer made of the polystyrene material is arranged and the heat absorbing layer made of the black waterproof material is arranged outside the heat preservation layer, the heat preservation function is achieved, and water is prevented from being frozen in the downpipe; due to the fact that the ribs in the horizontal direction are arranged inside the downpipe body, a rib structure is additionally arranged, and the strength of the pipe wall can be increased; due to the advantages, the service life of the downpipe in cold weather in the North China is prolonged.