The utility model discloses a brake device for an oil pumping unit, which is used in oil industry and aims to enable the braking process of the oil pumping unit to be labor-saving and reliable. The device comprises two brake hoops; the upper ends of the two brake hoops are hinged through a screw rod fixed on a reduction gearbox of the oil pumping unit; the device is further provided with a rocking lever and a rocking lever bracket; screw holes are formed at the lower ends of the two brake hoops, and threads in the screw holes are reverse threads; the rocking lever is mounted on the rocking lever bracket, wherein a rocking handle is arranged at one end of the rocking lever, and threads and a positioning ring are mounted at the other end; threads on the two sides of the positioning ring are reverse threads; and the two brake hoops are mounted on two sides of the positioning ring. When in rotation, the rocking lever drives the two ends of the two brake hoops to be folded and unfolded along the reverse threads on the rocking lever, so that braking of the oil pumping unit is realized; besides, the braking process is labor-saving, the combination is tighter, and safety and reliability are achieved; and consequences caused by untightness in combination of the brake hoops can be avoided. The brake device has the advantages of simple structure, easiness in manufacturing, reliability in working, and better use values.