The invention relates to a device used for increasing the stimulated Brillouin scattering threshold of a single frequency high-power fiber amplifier, belonging to the coherently combining field of the high-power broadband fiber amplifier and the fiber laser. In the device, heat fins (5) are unevenly distributed on the inside of a inner ring disk (1), a spiral groove is carved on the outside surface of the inner ring disk, an optical fiber enters the spiral groove from a short shaft arranged on the outside surface of the inner ring disk, rounds along the spiral groove, and extends form the short shaft arranged on the outside surface of the inner ring disk; inside surfaces of a left outer ring disk (2) and a right outer ring disk (3) are separately bound with the outer surface of the inner ring disk, two ends of the optical fiber enter or exit from a concave groove (61) in the left outer ring disk or a concave groove (62) in the right outer ring disk; one end of the left outer ring diskis connected and fixed with one end of the right outer ring disk though a bolt (9) and a nut (10), and the other end of the left outer ring disk is connected and fixed with the other end of the rightouter ring disk though a bolt (7) and a nut (8). The device of the invention can cleverly adapt to optical fiber with different lengths, is easy to install and dismantle, and can realize changes of the temperature and pressure of the optical fiber.