In order to verify the feasibility of keyhole gas tungsten arc welding（KTIG） technology in the field of offshore engineering equipment manufacturing,A36 and E36 steel plates for offshore engineering are root welded by KTIG,and filled and covered by submerged arc welding. The abilities of doublesided forming and deep penetration,and mechanical proper-ties of the welded joint of KTIG welding are studied and tested. It is verified that KTIG welding technology has good abilities of single-sided welding double-sided forming and deep penetration,and good tolerance of assembly clearance.The results show that the KTIG welding meets the general steel structure welding standards and offshore engineering equipment manufacturing industry standards. And it has a broad application prospect in the field of offshore enginee-ring equipment manufacturing.