Abstract: At present, weathering steels are developing rapidly in China, but most of them are used below Q345 grade, while weathering steels of Q500 grade and above are rarely used in engineering in China.Based on a comprehensive review of domestic weathering steel bridges, this paper calculates the corrosion resistance and carbon equivalent of Q500qENH high-performance weathering steel and corresponding welding materials, and analyzes their corrosion resistance and weldability, relying on the steel structure bridge project of G109 line reconstruction and expansion project, after calculation, the atmospheric corrosion resistance coefficient(I)of steel and welding materials is greater than 6, which indicates that the corrosion resistance is good, and the carbon equivalent(CE)of steel is greater than 40%, which indicates that the weldability of steel is still affected to some extent while the strength of steel increases.At the same time, the welding procedure of butt joint of Q500qENH high-performance weathering steel is evaluated, and manual arc welding and submerged arc welding are used re-spectively.Then, the welding procedure evaluation and inspection methods such as appearance evaluation inspection, ultrasonic testing, mechanical property test and macroscopic metallographic test are used respectively to analyze and evaluate its welding performance, and the welding procedure and welding parameters suitable for Q500qENH high-performance weathering steel are summarized, so as to provide experience and reference for the welding construction of similar projects.Highlights: In this paper, Q500qENH high-strength weathering steel is used as the lower flange plate of steel composite beam, and the welding process method suitable for Q500qENH high-strength weathering steel is studied and summarized.