The utility model discloses a vertical cone epicyclic gearbox of a sizing mill; the vertical cone epicyclic gearbox is formed by the mutual meshing of an input bevel gear pair in a lower engine body 14, a transmission teeth sleeve 4, a middle epicyclic gear pair in an engine body 13, an output epicyclic bevel gear pair in an annular gear II 12 in a three-level variable speed, wherein an input shaft 1 in the input bevel gear pair serves as the high-speed level input; a rotating stand I in the output epicyclic bevel gear pair serves as the low speed level output; central axes of a bevel gear 2 in the input bevel gear pair, the transmission teeth sleeve, the middle epicyclic gear pair and the output epicyclic bevel gear pair are superposed; and the input shaft of the input bevel gear pair vertically intersects with the bevel gear. A gear case is formed by a first-level bevel gear and a two-level epicyclic transmission and converts high revolving speed output by the electrical machine and small torsion into the low revolving speed and the high torsion so as to drive a working roll of the sizing mill to rotate; and the vertical cone epicyclic gearbox has advantages of simple structure, small volume, high efficiency, uniform loading of split flow, stable operation and good economy.