The invention provides an oil-throwing preventing protection device of a coupler and a use method of the oil-throwing preventing protection device and relates to the technical field of protection devices. The protection device comprises two half-sleeves. The joint of the coupler and a transmission shaft is sleeved with the half-sleeves oppositely, and the two half-sleeves are detachably connected through a connecting part to define a protection cover. The ends, close to the coupler, of the half-sleeves are coupling position sealing ends, and the other ends, close to the transmission shaft, of the half-sleeves are shaft portion sealing ends. The coupling position sealing ends of the half-sleeves are provided with coupling sealing parts, and the shaft portion sealing ends of the half-sleeves are provided with shaft portion sealing parts. The joints of the two sides of the two half-sleeves are provided with axial sealing strips respectively, and the ends of the axial sealing strips make contact with the coupling sealing parts and the shaft portion sealing parts. On the premise of not changing original design of the coupler, the applicable protection cover is additionally arranged, and adverse influences brought by throwing-out of lubricating grease are avoided. The oil-throwing preventing protection device is simple in structure, convenient to disassemble and assemble and capable of being reused.