The Front Floor is one of the parts in the car that has base (floor) of the front the car. Front Floor has a large dimension is (140 x 110 cm) from driver seat to the front passenger seat which is made of iron. In the assembly process, the front floor is arranged by type according to the demand on the production line. However, the line production asks the front floor to be inverted 180o from its originally position because to make easier assembly process. For that in the sorting process (minomi) a member needs to reverse the front floor using a manual way that requires a lot of power. Based on the problem, to tackled problems that occur made improvements on existing rotary dolly with semi-automation concept to facilitate members in rotating the front floor 180o. The methodology used is designing rotary dolly using semi-automation concept where the tool uses electric motor capable of rotate front floor equal to 180o. Then performed engineering calculations include the determination of motor power, the calculation moments at the critical point, the strength of welding, material selection, and the made the estimated cost of manufacture. The aids designed to specification of the front floor car types. The results of planning obtained for the improvement of rotary dolly with the concept of semi automation are as follows : length = 1650 mm, witdh =1442 mm, height = 1070 mm, rotation degrees = 180o, power source using electric motor, construction framework using square tube, solid shaft, and plate with the estimated cost of manufacutre Rp. 50.000.000,.