The invention discloses a vacuum heat insulation and preservation layer used for a building and provided with a steel mesh, a heat preservation system and a construction method. The vacuum heat insulation and preservation layer used for the building and provided with the steel mesh comprises a vacuum heat insulation plate for the building, a vacuum heat insulation bar for the building and the steel mesh arranged on the outer sides of the vacuum heat insulation plate for the building and the vacuum heat insulation bar for the building; fixing part preservation holes are reserved in outer sides of two ends of the vacuum heat insulation bar for the building and are filled with heat preservation materials; fixing parts penetrate through the fixing part preservation holes and the heat preservation materials and are used for fixing the steel mesh on a base wall. The vacuum heat insulation and preservation layer has the characteristics of excellent heat preservation and fireproof performance; the combustion grade is grade A; the specified requirements of energy-saving rate being 75% of the building can be met; meanwhile, when a surface layer is formed by objects with a certain weight such as ceramic tiles, marble slabs and mosaic tiles; the fixing parts and the steel meshes can be used for ensuring that the surface layer can be firmly mounted and are not liable to fall off.