The invention discloses a tunnel arch wall primary support limit-intruding arch-replacing construction method based on gantry-type supporting, which comprises the steps of: 1, temporary inverted archconstruction, i.e., constructing a temporary inverted arc construction in a to-be-arch-replaced section in a constructed tunnel, which needs to be subjected to arch replacement; 2, gantry-type supporting structure erection, i.e., erecting a plurality of gantry-type supporting structure for carrying out supporting on an arching which needs to be replaced on the temporary inverted arc; 3, arch replacement construction, i.e., beginning with an initial arch replacing end, removing a tunnel primary support structure in the to-be-arch-replaced section, synchronously carrying out primary support construction on the to-be-arch-replaced section in the removing process, and obtaining a tunnel primary support structure after replacement. The method disclosed by the invention is simple in step, reasonable in design, simple and convenient to construct and good in using effect, is based on the temporary inverted arc, adopts the gantry-type supporting structure, is high in structural integrity and firm in foundation, can effectively solve problems of inclination, collapse and the like of a tunnel arch-replaced steel frame, is safe and reliable in arc-replacing construction process and does not influence the tunnel construction progress.