Abstract: In order to achieve double width rolling of X70M linepipe-purposed steel plate in the direction of steel plate width,the microstructure type of the said steel plate as plasma cut and flame cut is studied,and thus the cuttingaffected range and the post-cutting microstructure distribution of the material are determined. And corresponding cutting method and steel pipe-welding process for double-width manufacturing of the linepipe-purposed steel plate are also worked out. The result shows that in case of good liquid steel cleanliness,plasma cutting process as used for the X70M steel plate just produces a small affected range of edge part,and causes no significant enlargement of the grain size,which has slight impact on welding of the linepipe. Using high energy welding is beneficial for improving the mechanical properties of the welding area so as to meet the requirements for the use of the X70M pipeline steel.