Abstract: Impact test results of heat-affected zone in welded joint of X70 pipeline steel were studied. The results indicated that impact absorbed energy of heat-affected zone in welded joint of X70 pipeline steel were proportional with shearing area on the whole. Impact absorbed energy was higher,shearing area was bigger. Impact fracture surface of heat-affected zone in welded joint included tough zone ,brittle zone and tough-brittle zone. Brittle zone was cleavage fracture,tough-brittle zone was quasi-cleavage fracture.