Abstract: In the light of the in-service welding technique of pipeline, from the viewpoint of influencing factors of control burning through and SCC, the paper describes regarding research situations at home and abroad. And research results in the safety of in-service welding and application of numerical simulation software in this field are introduced. Characteristics between ANSYS software and SYSWELD software in in-service welding simulation are compared. Problems to be solved in the research of this field are proposed.