The invention discloses a planet gear assembly manipulator. The planet gear assembly manipulator comprises a fixed disc and a movable disc arranged in parallel; at least two first connecting rods are uniformly arranged in the peripheral direction of the movable disc; second connecting rods corresponding to the first connecting rods are uniformly arranged on the fixed disc; the second connecting rods consist of first sub connecting rods and second sub connecting rods fixedly connected; angles formed by the first sub connecting rods and the second sub connecting rods are first angles; the second connecting rods are rotationally connected to the fixed disc; one ends of the first connecting rods are rotationally connected to the movable disc, and the other ends are rotationally connected with the first sub connecting rods corresponding to the second connecting rods; the fixed disc is fixedly arranged on a first bracket; and the movable disc is driven through a first driving mechanism to perform a reciprocating motion in the axle direction so as to drive the front ends of the second sub connecting rods to open and close. Compared with the prior art, the planet gear assembly manipulator has the advantage of capability of adapting to automatic assembly of planet gears with different sizes.