Phase-changed direct-cooling method is a novel efficient heat management scheme for fiber lasers. The cold-plate, as a critical component of the phase-change direct cooling system, significantly influences the temperature stability of the laser device. In this paper, three cold-plates are designed initially for the phase-changed direct-cooling system of a 2 kW fiber laser. Differences among the designs primarily arise from variations in cold plate fabrication methods. Afterwards, numerical simulations coupling fluid-heat-solid based on computational fluid dynamics are carried out to investigate the heat transfer performance of the cold-plates. The results indicate that the cold-plate, which incorporates finned ribs in certain areas of a single-layer channel, achieving a peak surface temperature of 27.13 ℃ and an average temperature of 24.56 ℃. Its average heat transfer coefficient is 78% higher than that of the designed perforated serial-parallel channel configuration, demonstrating superior thermal performance. This design effectively reduces the operating temperatures of key fiber laser components. Moreover, the mass of the cold-plate is reduced by 47.64% compared to the parallel and series channel design, contributing to the lightweight design objectives for high-power fiber laser products.