Abstract: Online repairing the welds for newly-built oil and gas pipelines will be necessary if different welding defects are detected before commissioning, For the repaired welds after twice welding, heating and shrinking, hot and cold cracks will be formed; or they would tend to produce greater internal stress and lead to cause accidents, Therefore, For Grade L415, X60, X70 and X80 steel pipe, preheating on the welds to be repaired should be carried out before welding, And some measures should be taken to keep the welds warm after welding if temperature is below 0℃, The qualified rate of the first time repaired welds should be improved to avoid the project costs from increasing, which is induced by welds cutting and re-welding, Some requirements for welds repair are given including weld preparation, technology specifications, welding parameters and environmental conditions.