The invention discloses an arc bridge reinforcing method for improving structural resistance. The arc bridge reinforcing method comprises the following steps that (1), reinforcing steel bars of an arch crown area are welded to the upper edge surface of an arch crown, when the steel bars are positioned, concrete pouring is carried out in the arch crown area, a light concrete layer is laid on a concrete layer, and then bridge deck pavement is carried out; (2), a zero-point line of a bending moment is detected and calculated; (3), reinforcing steel bars of an arch foot area are welded to the upper edge surface of the arch foot area, when the steel bars are positioned, pouring work for enlarging a cross section area of the arch foot area is carried out; and (4), reinforcing steel bars of the arch crown area are welded to the lower edge surface of the arch crown area, and when the steel bars are positioned, concrete pouring is carried out. According to the arc bridge reinforcing method, dead load is not increased, resistance of the arch crown is increased, height and area of the cross section are increased, resistance of the arch foot is increased, cross section area of the arch foot isincreased, self-weight of the arch foot is increased, so that arch pressing effect is achieved, sagging moment of the arch crown is reduced, the aim of adjusting arch axis pressure line is achieved,and resistance of the cross section of the arch crown is improved.