Abstract: From the mechanical property and welding defect points of view,weldability of crack free low carbon bainite steel ADB610 and WDB620 are studied.Based on weldability test in three weld methods,it is indicated that weld joints have better tensile strength,bending property and impact toughness.Welding defects of steel ADB610 and WDB620 weld joints on the X-rays negative film in three weld methods are analyzed.With Pareto diagrams of defects type being drawn and analyzed,it is found that the main defects types are air hole and slag inclusion,and the crack is very seldom,which indicates that steel ADB610 and WDB620 have little crack tendency.