With the progress of science and technology,the welding of large structural parts has been greatly improved,but the welding of heavy load bases with high-quality welds and complex structures is still a big problem. Welding defects still accompany the entire welding process, and the quality of weld is difficult to meet the requirements of grade Ⅰ in QJ176B-2016"Technical requirements for fusion welding of land-based facilities", and the long-term load use of the base has safety risks. For this problem, a certain product base is taken as an example, the welding method selection, welding process control, stress relief and other aspects are analyzed and researched, and a set of technological method that can improve the quality of weld and reduce the deformation is proposed. By using these methods, the welding of the base achieves remarkable results, and the qualification rate of radiographic inspection of grade Ⅰ weld reaches 90%. The successful use of this method in the heavy load base provides reference for the welding of large frame type structural parts with high weld quality requirements.