The invention discloses a robot device and a motion control method thereof. The robot device comprises a joint type mechanical arm, a rotating shaft allowing a joint of the mechanical arm to rotate and a main engine for driving the rotating shaft. The control method for controlling the rotating shaft by the main engine comprises the steps of firstly, acquiring the current position of the rotating shaft and the target position of the rotating shaft, then performing point-to-point motion, and calculating the position of the rotating shaft. According to the robot device and the motion control method thereof, the position of the rotating shaft can be calculated at the same time when the point-to-point motion is performed so that when the motion track of the mechanical arm is likely to exceed the working range, the main engine can correct the motion of the rotating shaft in real time, and therefore the motion track of the mechanical arm can be effectively prevented from exceeding the working range.