Abstract: The impact test results of heat affected zone of welded joints of high-grade pipeline steel were more dispersive. In order to study the influence factors of impact absorption energy fluctuation, the impact test results of fusion line position of welded joint of X70 submerged arc welded steel pipe were analyzed. The results show that the impact absorption energy by the fusion line in heat affected zone of welded joint of X70 submerged arc welded steel pipe was low, but the average impact absorption energy by the fusion line was over 100 J at the test temperature of -10℃. The significant fluctuation of impact absorption energy by the fusion line in heat affected zone of welded joint of X70 submerged arc welded steel pipe was caused by the deviation of groove position and the uncertainty of crack propagation direction.