The invention discloses a herringbone-tooth planetary transmission device, which comprises a sun wheel, a planet wheel and an inner tooth ring, and is characterized in that herringbone teeth are respectively adopted by the sun wheel, the planet wheel and the inner tooth ring; a planet carrier is fixed, and the planet wheel only rotates without revolution; the inner tooth ring and the sun wheel respectively rotate around own axes; the inner tooth ring is a combined-type segmented herringbone inner tooth ring and is formed by combining and connecting two or more than two single-segment herringbone tooth rings through hinge-hole bolts which are forwards and backwards arranged; the left and right turning wheel teeth of the single-segment herringbone tooth rings are respectively formed through integral machining, and a direct horizontal-cutting segmenting mode is adopted. The herringbone-tooth planetary transmission device has the beneficial effects that the assembly of herringbone-tooth planetary transmission is realized, the reliability of a transmissions system is improved, the assembling precision is guaranteed, the inner tooth ring with a large diameter can be obtained on a smaller machine tool through segmented machining, the machining process and the assembling process are mature, simple and feasible, the transporting, packaging, assembling and disassembling processes are quite convenient, the maintenance and the replacement of the single-segment tooth rings can be realized, and therefore a large number of materials and machining expenses are saved.