The invention discloses a heat insulation protection layer of a pipeline and a construction method thereof. The heat insulation protection layer comprises a heat insulation layer, a protection plate,half headers, sealants and a protection layer, wherein the heat insulation layer covers the outer side of the pipeline; a covering layer covers the outer side of the heat insulation layer; the half headers are arranged on two sides of the covering layer and are sealed through the sealants; the half headers are right-angled L-shaped annular angle irons; one ends of the heat insulation half headersare perpendicularly welded onto the pipeline; the size of the connecting position of the upper end of each heat insulation half header and the covering layer is 200 to 300mm; and the protection layeris arranged on the outer sides of the heat insulation half headers and the covering layer. The invention provides a construction method. According to the heat insulation protection layer of the pipeline and the construction method thereof provided by the invention, the heat insulation protection layer is simple in structure and convenient to use, the service life is prolonged, the heat insulationeffect is improved, and the weather resistance, the corrosion resistance and the water tightness of the heat insulation protection layer are improved.