The invention discloses a double-limb triangular hanging basket and construction method for a large-span continuous rigid frame bridge cantilever beam segment. The hanging basket comprises a travelling system, a primary truss, a formwork system, and a lifting and hanging system. The primary truss and the formwork system are connected together through the lifting and hanging system. The primary truss comprises a front upper cross beam, a rear upper cross beam, and two truss groups which are symmetrically distributed on the left side and right side of a cantilever beam section. Each truss groupcomprises two triangular trusses which are arranged side by side. The lifting and hanging system comprises a bed die lifting and hanging structure, a side die lifting and hanging structure, and an inner die lifting and hanging structure. The double-limb triangular hanging basket is used in the method to respectively perform construction on the cantilever beam sections of a cantilever beam segmentfrom right to front. The truss groups formed by two triangular trusses side by side are used to solve a load carrying problem of a hanging basket primary truss in a large-tonnage cantilever beam segment construction process. After the truss group is divided into two parts, the truss group can be used as a conventional hanging basket. A bed die adjusting structure and a pulling type inner die trussare used, and simple and rapid construction requirements of a variable section beam can be satisfied.