In order to sovle the problem of line control and error adjustment of steel box arch in the construction of medium-bearing tied arch, Qingfu Port Bridge in Maoming City, Guangdong Province, which is a medium-bearing tied arch bridge, is taken as the research background, and the position control and load control of its bracket design are studied, and optimised and adjusted according to the results of on-site calculations. For the error of mileage and elevation during the installation process, a method of adjusting the line shape in stages with welds is proposed. The research results show that the error adjustment method can ensure the smoothness of the bridge line and better control the state of the internal force of the formed arch. This study can provide a reference for the linear control of arch bridges with similar construction methods.