The invention discloses a hydro-viscous transmission device, which comprises a box body, a speed regulating mechanism and a braking mechanism, wherein the speed regulating mechanism comprises a speed regulating shaft, a speed regulating shaft transparent cover, a driving friction plate, a driven friction plate, a driven drum, a driven disc, a first piston cylinder, a third piston cylinder and a first control oil pipe, and the braking mechanism comprises a braking shaft, a braking shaft transparent cover, a movable friction plate, a static friction plate, a braking drum, a braking disc, a second piston cylinder, a fourth piston cylinder, a second control oil pipe and a third control oil pipe. The hydro-viscous transmission device has the advantages that the ingenious structure is adopted, the design is simple and reasonable, a stepless speed regulation function of a hydro-viscous speed regulating clutch and a braking speed reduction function of a hydro-viscous brake can be simultaneously realized on a set of device, in addition, the work speed regulating performance and the service life of the device can be obviously improved and prolonged, and the hydro-viscous transmission device is particularly suitable for occasions that a high-power work machine simultaneously needs two kinds of work conditions of speed regulation and braking.