The invention discloses a construction technology for a heat insulation outer wall. The construction technology has the following technological processes that an interface mortar layer is coated on the surface of a base layer wall; glass fiber spraying cotton and a special spraying adhesive are mixed and sprayed on the surface of the interface mortar layer to form a first heat insulation layer; then grid cloth covers the first heat insulation layer and is stretched to be flat in the horizontal direction, and the grid cloth is pressed in the heat insulation layer by using a trowel and fully pressed to be flat; after the heat insulation layer is solidified, the glass fiber spraying cotton and the special spraying adhesive are mixed again and sprayed at the exterior of the grid cloth to forma second heat insulation layer; and waterproof and anti-cracking mortar is sprayed at the exterior of the second heat insulation layer again, and a first waterproof and anti-cracking mortar layer is formed after being flattened. The outer wall has the advantages of being good in heat insulation efficiency, high in structural strength and high in anti-cracking performance.