The invention discloses a construction method of door opening arc section capping in a large-span portal type high pier, and relates to a construction method, in particular to the construction methodof the door opening arc section capping in the large-span portal high pier. The defects that are existed in an traditional construction method of the door opening arc section capping in the large-spanportal high pier, such as the construction technology is complex, the precision is not easy to be controlled, the steel consumption is large, the dependence on large hoisting equipment is strong, andthe occupied effective construction period is long are aimed to be solved by the method. The method comprises the following steps that an arch-shaped supporting system is machined according to the size of a main body structure; a wooden box is embedded in the position where a foundation beam is located when the concrete construction of the main body is constructed, cross beam brackets are inserted after a template and the wooden box are disassembled, and the middle cross beam and the cross beam brackets are connected to form the foundation beam; wedge blocks are mounted, and elevation adjustment is unified by placing steel plates on the wedge blocks; cis-bridge direction distribution beam is installed, and the distribution beam is used for distributing the upper load, so that one group of multi-piece foundation beams are enabled to be consistent in stress; single-splicing arch frames are mounted; and the method belongs to the field of road bridge construction.