The invention discloses a three-branch-chain six-degree-of-freedom parallel mechanism with an arc-shaped moving pair. The three-branch-chain six-degree-of-freedom parallel mechanism comprises a base, a motion platform and three similar motion branch chains, wherein the motion branch chains are mounted between the base and the motion platform in a radial and uniform distribution manner, and comprise first arc-shaped connection rod assemblies, first motors and supporting connection rods; one end of each supporting connection rod is hinged to the motion platform; one end of each first arc-shaped connection rod assembly is hinged to the corresponding supporting connection rod; each first motor is arranged on the base and used for driving the corresponding first arc-shaped connection rod assembly to rotate; and the arc length of each first arc-shaped connection rod assembly changes with the rotation of the first arc-shaped connection rod assembly.