The invention discloses a compact heavy belt driving device for liquid viscosity speed regulating, and aims at solving the problems that an existing heavy belt driving device wastes resources and is large in size, complex in structure and high in using and maintaining cost. The compact heavy belt driving device for liquid viscosity speed regulating comprises an input shaft, an inner gear ring, a first sun gear, a second sun gear, a first-stage planetary gear, a second-stage planetary gear, first pin shafts, second pin shafts, a first gear holder, a second gear holder, a large cover, a left boxbody, a right box body, a support, a rack, a roller shaft, a liquid viscosity assembly and a roller; an involute inner gear is machined at the tail end of the input shaft, the inner gear meshes withthe first sun gear, and the first sun gear meshes with the first-stage planetary gear; and the first pin shafts are installed in inner holes of the first-stage planetary gear through first bearings, and the multiple first pin shafts are installed in corresponding holes of the first gear holder and drive the first gear holder to rotate in the axial direction of the first sun gear. The compact heavybelt driving device for liquid viscosity speed regulating is used for heavy belt driving.