The invention discloses a floating floor slab of a high-rise building large scale device and a construction method. The construction method comprises the steps of arraying and densely distributing plural vibration isolation rubber mats on a structural floor slab in an equal interval mode, arranging plural galvanized channel steel above the plural vibration isolation rubber mats in a covered mode, wherein the upper ends of the vibration isolation rubber mats are embedded into grooves of the galvanized channel steel, and the galvanized channel steel is parallel to one side of a structural wall body, laying plural galvanized sheets above the galvanized channel steel in a full mode, binding steel bars of a device foundation floor slab on the galvanized sheets, pouring the concrete of the device foundation floor slab so as to form the floating floor slab, and arranging an elastic rubber mat between the floating floor slab and the structural wall body, wherein the elastic rubber mat serves as a partition surrounding edge rubber plate for isolation of rigid connection. The floating floor slab is born by the structural floor slab. But, a support component with elasticity formed by utilizing the vibration isolation rubber mats enables the device foundation floor slab and the structural floor slab of the floating floor slab to be completely separated. The portion below the structural floor slab is quieter than the time when impact directly falls onto the structural floor slab.