The invention discloses a C-shaped mold closing mechanism. The C-shaped mold closing mechanism comprises eight boost oil cylinders, four flashboard devices, a middle heat plate, a C-shaped body frame, an upper movable template and a lower movable template; the eight boost oil cylinders use hydraulic pressure as a power source, and are respectively two long mold closing boost oil cylinders, two short mold closing boost oil cylinders and four quick mold closing oil cylinders; the two long mold closing boost oil cylinders and the two short mold closing boost oil cylinders are arranged on the upper movable template; the four flashboard devices are arranged on the lower movable template; and the upper and lower movable templates are respectively in drive connection with the four quick mold closing oil cylinders. The C-shaped mold closing mechanism finishes the mold machining, can satisfy multiple machining conditions of double molds, mold closing and vulcanization while providing large-tonnage mold closing force, uses the upper and lower movable templates for molding upper and lower two sets of mold products to the middle heat plate through mold closing, can adapt to the two sets of molds with different mold thicknesses through adjusting relative positions of the middle heat plate and the upper and lower movable templates, can synchronously mold the two sets of molds up and down, and can finish one complete product through two times of molding.