Abstract: The door frame and tower are the most important rigid support components of the wind turbine, and the door frame and the tower angle joint are the stress concentration position. The welding production quality requirements are high,and nondestructive testing is strictly carried out before leaving the factory, but it is still found that some of the wind turbine door frame and tower welding joints that have been in service for several years have excessive defects, which seriously affects the safe and stable operation of the wind turbine, and the on-site repair must be completed in time and rapidly.Comprehensively considering that the site does not have the conditions for post-weld heat treatment, the process test of gas metal arc welding（MAG） and tempering welding beads of low-alloy steel Q345E was carried out, and the visual inspection,tensile test, bending test, impact test, macroscopic metallographic inspection and hardness test of the welded joint were carried out. The results show that the MAG welding and adding tempering weld beads is suitable for the on-site repair of the door frame and the tower welding joint, the joint has no defects, and the mechanical properties of the joint are good, the-40 ℃ low temperature toughness and microhardness are good, and the repair efficiency is high.