The invention relates to a parallel mechanism of a four-degree-of-freedom dual acting platform, belonging to the field of industrial robots. The parallel mechanism comprises a fixed platform, a movable platform, and four branches for connecting the fixed platform and the movable platform, wherein the movable platform comprises an upper movable platform and a lower movable platform, which are parallel, and further comprises a connecting mechanism for connecting the upper movable platform and the lower movable platform, a rotating mechanism, and an end effector; the connecting mechanism comprises three or four planar quadrilateral mechanisms, which are uniformly arranged and connected between the peripheries of the upper movable platform and the lower movable platform. According to the invention, by adopting the planar quadrilateral mechanisms, the upper movable platform and the lower movable platform are reasonably connected, and the mechanism has effective supporting and guiding actions; by utilizing the over-constrained characteristic and the high rigidity characteristic, when the upper platform and the lower platform move relatively, the directional stress is uniform and the rigidity is unchanged, and the rigidity and the stability of the parallel mechanism of the integrated machine are improved; furthermore, the motions of the quadrilateral mechanisms are in the respective plane, so that the structure is more compact.