Two kinds of roll casters, which were suitable for high speed roll casting, were devised. One was a vertical type twin roll caster, and the other was an unequal diameter twin roll caster. The semisolid roll casting using a cooling slope was adopted to these roll casters. The solid fraction was smaller than 5%. 3 mm thickness of 6111 strip was cast at 60 m/min by the vertical type twin roll caster, and 5 mm thickness of 6111 strip was cast at 30 m/min by the unequal diameter twin roll caster. The microstructure of the as-cast strip was equiaxed and spherical, not columnar. The mechanical properties of the strip rolled from roll-cast strip were almost as same as that of the strip made from cast ingot.