Abstract: The K-TIG welding technology was used to weld the 10 mm thick Q235 steel. The results showed that the welding process was stable, and the welded joint with good weld formation and no defects such as cracks and pores was obtained. The dynamic behavior of keyhole in the welding process was observed by high-speed photography test, and the microstructure and hardness of the welded joint were studied The mechanical properties such as tensile, impact and bending are tested. The results show that the stability of keyhole of K-TIG welding can be increased by improving the heat dissipation condition and reasonable assembly clearance; the Vickers hardness of weld area and heat affected area are higher than that of base metal; the tensile strength and impact toughness of welded joint are better than that of base metal; the weld area is mainly composed of fine acicular ferrite and a small amount of massive ferrite The K-TIG welding joint with excellent properties has been obtained, which has reference significance for the further study of K-TIG welding process of low carbon steel.