To address the issue of mutual interference between the front legs of the bridge crane, which hinders its ability to meet beam erection requirements, a design scheme for the front legs of an ultra-wide highway bridge crane was presented. Through theoretical analysis, three-dimensional modeling and finite element analysis, a new structure scheme of the front legs of the bridge erecting machine was proposed, which realizes the independent movement of the two front legs. In this scheme, the traditional pure box structure was transformed into the main leg, the hydraulic lifting leg and the auxiliary leg. Through the adduction of the front leg, the bridge erecting machine's front leg can be raised onto piers with standard diameters. By incorporating an opening and closing structure design for the front leg, it allows unobstructed passage for ultra-wide beams. Consequently, the innovative solution effectively resolves technical challenges encountered during construction of steel mixed bridges in Guizhou Province, enabling efficient installation of entire ultra-wide continuous steel main beams. The safety performance of the bridge erecting machine structure designed is verified through finite element analysis and field stress and deflection monitoring. The verification is exemplified by the laying of Xinpinghe Extra-large Bridge on Du'an Expressway in Guizhou Province, providing a valuable reference for the application of ultra-wide highway bridge erecting machines.