Cutting arm of thin seam mining machine

The utility model provides a cutting arm of a thin seam mining machine. The cutting arm comprises an arm frame, and a cutting motor, a clutch mechanism, a primary straight tooth speed reducing mechanism, a secondary straight tooth speed reducing mechanism, a primary planetary mechanism and a secondary planetary mechanism which are positioned in an inner cavity of the arm frame. Heat exchange devices are arranged between a first cavity where the first-stage straight-tooth speed reduction mechanism is located and a second cavity where the second-stage straight-tooth speed reduction mechanism is located, and heat exchange devices are arranged between the second cavity where the second-stage straight-tooth speed reduction mechanism is located and a third cavity where the first-stage planetary mechanism and the second-stage planetary mechanism are located, so that lubricating oil can flow and exchange circularly. And the heat dissipation capability of the cantilever crane is improved. The side wall of the lower po