Abstract: A certain DC03 steel had lack of welding defects in spot welding. The causes of lack of welding defects in material spot welding were analyzed using methods such as chemical composition analysis, mechanical performance testing and metallographic examination. The results show that the material had a higher carbon content and higher hardness, which affected its welding quality. By adjusting the steelmaking process, reducing carbon content and adjusting the thickness of hot－rolled raw materials, the welding quality of the product could be effectively improved.