The invention relates to a variable Mach number nozzle mechanism having large-stroke range and high precision. The mechanism includes a rigid-flexible coupling profile 1, a rotation support plate 2, an arc rolling sliding block 3, a support plate hinge 4, a smooth guide rail 5, a sealing supporting plate 6, a ballscrew electric cylinder 7, an electric cylinder hinge 8, and a nozzle fixing rack 9, wherein the rigid-flexible coupling profile 1 includes a fixed profile section 1-1, a flexible profile section 1-2, and an exit straightening section 1-3. According to the invention, the mechanism has a simple and compact structure, and overcomes low control precision caused by multiple procedures, such as force transmission, machining and assembling, etc. The mechanism combines the rolling arch guide rail and a ballscrew electric cylinder, which effectively guarantees non-linear control precision and repeatability. The mechanism achieves continuous adjustment of Mach number, is tightly constructed, has strong practicality and allows easy engineering and design for thermal protection and pneumatic sealing.