The three suction pump dredgers built at Hitachi Sakurajima Shipyard last year have adopted the new launching method called “Wire loosing and winding method”, by launching her slowly with wires which is rather different from the common sliding method. The new method was adopted because : (1) The ship type is an Ark. (2) All the outfittings were installed on the building way and her launching weight will be about 1, 000 ton. (3) Having special apparatus as the suction ladder and spuds on her fore and aft. Under these conditions, the authors have considered of using this new methods not to cause any damage to the ways and to the side walls, also not to change the sliding direction by water stopping resistance, tidal current and wind pressure that work unequally to each part of her. The launching way for the wire loosing and winding method was exactly the same as ordinary ships in using greases, but the chocking, loosing, winding and adjusting were all done from the ground by wires. The authors have measured the tensile force which worked to the parts during the launching. These figures were submitted for reference to safety launchnig work and also it was checked and compared with the planned figures for the future reference. The authors have confirmed at least that the arrangement and mechanism of the apparatus have met its purpose. When the keel blocks were taken off, the authors found that the direct working tensile force was larger than its plan but the grease frictional coefficient was rather smaller than its plan showing 0.002-0.007, therefore the author consider that the dredger was in very easy condition to slide. During loosing and winding the authors have noticed that the shock load did not work so much in this case but if the apparatus are not closely associated with its operation, she would become unbalanced by a large load that cannot be expected which is the most warning point for this dredger launching.