The invention discloses a six-degree-of-freedom serial-parallel mechanism which comprises a base, a first motion platform, a second motion platform, three first motion branch chains and three second motion branch chains, wherein the three first motion branch chains are connected between the base and the first motion platform respectively to form a first parallel mechanism; and the three second motion branch chains are connected between the first motion platform and the second motion platform respectively to form a second parallel mechanism. According to the six-degree-of-freedom serial-parallel mechanism, the structure is symmetrical, and the assembly is convenient and accurate; the first parallel mechanism and the second parallel mechanism share the first motion platform to form the serial-parallel mechanism, and the defect that the work space of the parallel mechanisms is small is supplemented through a serial mechanism; the second motion platform has six degrees of freedom relative to the base, and the six-degree-of-freedom serial-parallel mechanism is applicable to the working conditions such as manufacturing, assembly and material picking.