The invention relates to a pipe hydraulic forming technique, particularly to a technique for high-pressure mold-filling bulging in an internal spiral curved surface. A workpiece is positioned and clamped on a workbench, two ends of the workpiece is sealed by a sealing device, an electric heating device is started, the workpiece is filled with a high-pressure liquid, and the workpiece begins to bulge freely. Then the electric heating device is removed from the workbench after being turned on, an internal spiral curved surface mold is closed, and after a detection device detects that the workpiece is completely attached to the mold, the pressure is kept for a certain period according to geometric dimensions and the material of the workpiece. After completion, a hydraulic system is unloaded, the workbench is inclined to enable the liquid to flow back quickly, the sealing device is opened, and the workpiece is taken down. The devices adopted in the technique are simple in structure and low in cost, and molding of a pipe with the internal spiral curved surface is realized; efficient machining of internal spiral curved surfaces of spiral stator cases can be realized with the technique; the machining efficiency is multiple times that of an existing machining technology. The technique can be applied to production of other pipes with the internal spiral curved surfaces.