The invention discloses a high-power optical fiber high-efficiency cooling device and method capable of achieving the mode loss control, and the device comprises a high-power optical fiber, a hollow metal fine tube, a heat sink containing flowing cooling liquid, and a heat conducting medium. The high-power optical fiber enters from one end of the metal fine tube, and comes out from the other end of the metal fine tube. The heat conducting medium is disposed between the high-power optical fiber and the inner wall of the metal fine tube in the metal fine tube where the high-power optical fiber passes through. The heat of the high-power optical fiber is uniformly conducted to the metal fine tube through the heat conducting medium. The heat sink is provided with interfaces which are used for the fixing of two ends of the metal fine tube, and the high-power optical fiber is bent for inserting, and is put in the flowing cooling liquid in the heat sink. Two ends of the metal fine tube are respectively fixed at the interfaces on the heat sink. According to the invention, the device achieves the uniform and high-efficiency heat dissipation for the high-power optical fiber, and achieves the control of the laser mode loss of the optical fiber through the random bending of the optical fiber in a certain range.