The invention discloses a manufacturing method of a rotary-cutting device for high-viscosity polymer gel. The manufacturing method includes steps of (1) manufacturing a connecting rod, two to four concave vanes and an electric driver, wherein the upper end of the connecting rod is shaped in a hexagonal prism, the connecting rod is 8-10mm in outer diameter and 350-450mm in length, the concave vanes are identical in specifications, 120-150mm in unfolding length, 20mm in width and 1.5 in thickness, the concave vanes are upwardly or downwardly bent from the position away from the center by 1/2-3/5, and each bending angle ranges from 30 degrees to 60 degrees; (2) crossly welding the 2 to 4 concave vanes to form a stacked concave vane, wherein the two ends of the concave vanes when the concave vanes are stacked are upwardly bent, or downwardly bent or some are upwardly bent and some are downwardly bent, and the lower end of the connecting rod is fixed at the centers of the concave vanes through a thread; (3) fixing the electric driver as a driving device at the upper end of the connecting rod. The rotary-cutting device is simple in structure, the concave design of the vanes improves axial cutting action of the rotary-cutting device, and the stacking design of the same further enhances the cutting action.