The invention provides a construction method of a totally closed layer in a super high-rise building core cylinder. The construction method comprises the steps that in the construction process of thesuper high-rise building core cylinder, when a core cylinder vertical wall exceeds an external frame steel structure by a plurality of storeys, and the external frame steel structure exceeds an internal cylinder horizontal structure by a plurality of storeys, the two ends of a first high altitude gallery are arranged on a first connecting beam and a second connecting beam of the core cylinder vertical wall correspondingly, and the first connecting beam and the second connecting beam are opposite to each other. A first cross beam and a second cross beam are transversely arranged on the left side and the right side of the first high altitude gallery correspondingly, and the first cross beam and the second cross beam are connected with the first high altitude gallery and the core cylinder vertical wall correspondingly. The first cross beam and the second cross beam are paved with a plurality of first face plates correspondingly. The construction method is ingenious in design, easy, convenient and rapid to operate, and low in cost. The constructed totally closed layer can bear large loads, the requirement for force bearing of a vertical steel pipe formwork is met, an up-down perpendicular operation face is provided, an internal cylinder can be divided to two construction sections to be constructed independently up and down, the construction safety is ensured, the construction period pressure is relieved, and the construction method is suitable for being applied and promoted in a large scale.