The invention provides a PVC (Polyvinyl chloride) protective corner technology for an external corner in heat insulation construction of an exterior wall. The technology comprises the following steps of laying a finished PVC protective corner with double-wing mesh cloth at each position of external corners, such as large external corners, windows, cornices and holes, of a wall surface before surface mortar is plastered on the exterior wall for heat insulation for the last time; arranging a through line at each external corner position; firstly plastering rendering putty on the bottom layer, adjusting the protective corner installation position according to the through line, pressing the double-wing mesh cloth, then plastering wall surface putty and pressing glass fiber mesh cloth, and plastering the surface mortar for the last time. The PVC protective corner technology for the external corner in the heat insulation construction of the exterior wall has the advantages that the heat insulation quality and acceptance check of the exterior wall conform to standard error requirements, the sealing property and safety of the exterior heat insulation system of the exterior wall are improved, and the durability of the exterior heat insulation system of the exterior wall is guaranteed; meanwhile by utilization of the protective corner, the construction speed is increased, the construction period can be shortened, the labor cost is reduced, the construction cost is reduced, the impact resistance of the external corner is improved, a wall corner is effectively prevented from being damaged, the appearance quality is improved, the construction quality is improved, and the service life of the exterior wall for heat insulation is prolonged.