At present,manual arc welding is the main welding method for the circumferential seam of steel containment vessel（material is SA738 Gr.B） in CAP1400 nuclear power plant,which is not only inefficiency,but also high cost. The submerged arc horizontal position welding technology test is carried out under the condition of heat treatment and non-heat treatment respectively,and the results of welding material applicability,specimen preparation requirement,nondestructive testing,machining sampling and destructive test are analyzed. The results show that the welding material and reliable submerged arc welding technology adopted can meet the welding technology requirements of SA738 Gr.B steel plate. So the submerged arc horizontal position welding technology can be used for the welding of the circumferential seam of nuclear power plant steel containment vessel.