P355 NL1 low alloy steel is a commonly used material for bogie frame. In this paper,the tensile,impact,flexural and fatigue tests of the welded parts of P355 NL1 low alloy steel and its repairing part are carried out. The result shows that it’s not bad for microstructure of welding repair and the grain size of the retained lower welding layer can be refined. There is no obvious decrease in the welding hardness after single pass welding. The tensile failures of the two parts happened on the base metal,the welding repairs have no effect on the static load strength. Comparing with original welding part,due to the welding of the last remaining welding joints parts played a role in heat treatment,grain refined,improved tissue distribution,the impact toughness and fatigue strength of repairing part is improved.