High-power fiber lasers usually use water-cooled heat dissipation methods for temperature control, which are difficult to meet the needs of light. By using the characteristics of phase change energy storage materials and multi-phase change temperature control technology, the volume and weight of high-power fiber laser systems can be greatly reduced. In this paper, the temperature control technology of the fiber laser is analyzed, and the multi-phase change temperature control technology is used. The all-fiber laser output with a wavelength of 1.08 μm and a maximum power of 1.26 kW is achieved. The light-light efficiency is 75.4%, and the beam quality is M_x²=1.21, M_y²=1.23. The volume and weight of the laser is effectively reduced. It provides a new method for thermal management of high-power fiber lasers.