Abstract: A planetary limit switch contains a front transmission module, at least one following transmission module, and at least one micro switch. The front transmission module couples with an external power source and includes a first planetary gear carrier and plural first planetary gears for matching with the first planetary gear carrier, a front driving gear meshes with the plural first planetary gears and connects with a driving shaft so as to be driven by the driving shaft. Each following transmission module includes a second planetary gear carrier and a plurality of second planetary gears, and the plurality of second planetary gears meshing with a following gear, wherein the second planetary gear carrier has a cam portion arranged on an outer peripheral side thereof. The at least one micro switch is fixed below at least one following transmission module and touched by the cam portion of the second planetary gear carrier.