Abstract: Continuous cooling transformation diagrams (Welding CCT diagrams) of hot-affect zone in hot rolled steel plate were developed to investigate the welding properties of hot rolled shipbuilding plate.According to them,the reasonable welding technique was selected to weld hot-rolled shipbuilding plate (10mm thick) through manual arc welding and welding joints after the welding process were measured by visual examination,X-ray inspection,mechanical property and impact tests.Microstructure at different cooling rates on CCT diagram,microstructures in welded joints and impact fracture morphologies were analyzed by means of metalloscope and scanning electron microscope.As a result,it is indicated that the manual arc welding technique is reasonable since good quality of welding seam and excellent complex properties in welded joint.