The main beam of No. 7 extralagre Bridge Crossing Qingjiang River is of insitu cast continuous cantilever beam of prestressed reinforced concrete with single box and single chamber. The main span of the bridge is 88m, which at present is the largest for single track railway bridges ever built in China. The width/span ratio of the bridge reaches 1/20, which is the limit of the specifications. There exist great risks and difficulties in the construction of the bride. Travelers are fundamental equipment for the construction of the bridge cantilever beams. The article places its emphasis on the presentation of the design and construction of the travelers, as well as the items to which specail attention should be paid during construction.