The utility model relates to well head equipment of a pumping well in an oil field, particularly to a thievery prevention device for a motor fixing bolt. A motor base is fixed on a motor track through a motor fixing bolt group, an insertion block is inserted into the lower part of the side plate of the motor base, two symmetrically arranged connectors are tightly attached on the side plate of the motor base, an insertion pin at the lower part of a disassembly prevention cover is inserted into an insertion slot on each connector, the disassembly prevention cover is arranged on each connector and is provided with an open slot and a window, the width of the window is larger than that of the open slot, the width of the bolt is larger than that of the open slot and is smaller than the width of the window, a bolt base is arranged on the inner bottom surface of each disassembly prevention cover, the male threads of the bolt are connected with the female threads of the insertion block, and two symmetrically arranged thievery prevention sleeves are fixed at one ends of the connectors and sheath the motor fixing bolt group. The thievery prevention device is fixed by virtue of a motor structure, so that thieves can not disassemble the motor fixing bolt group and can not stole the motor and pumping unit accessories, thereby avoiding various economic losses due to the motor of the pumping unit being stolen.