Abstract: When in-service pipeline welding is carried out under low temperature environment, the medium within the pipeline will flow away some welding heat and in addition, the external low temperature environment will also speed up the cooling of welding seam, thus increasing the probability of pipeline welding hydrogen-induced cracks in in-service pipeline. Main control measures to guarantee the welding quality of in-service pipeline under low temperature condition include: adopting interpass temperature control by changing the preheating way of welded seam, using tempering welding bead process to improve the environment temperature, strengthening the delayed detection of hydrogen crack and adopting heat preservation after welding, etc. Because of the improvement in pipeline steel quality and differences in manufacture processes, the influence of low temperature environment on the weld cold crack of in-service pipeline becomes more complex. Therefore, in-depth research on the welding process of in-service pipelines of different steel quality under low temperature and different operating conditions is carried out.