Abstract: The influence of segments heat source and mesh size on calculation accuracy and efficiency of 3-D EFA of multi-pass butt-welded pipe were investigated.The methods can meet the demand of calculation accuracy and high efficiency of 3D finite element simulation of large pipes.The results show that the mesh size below or equals to 3.3mm can meet the accuracy requirement,the segment heat source,which has little efficiencies on calculation accuracy,can improve the calculations efficiency greatly.