The invention relates to a power synthesis device, in particular to a high-power optical fiber power beam combiner. The high-power optical fiber power beam combiner comprises N (N is greater than 1) input optical fibers, an output optical fiber, a shell, matching liquid and a matching liquid exchange device, and is characterized in that the optical axes of the N input optical fibers are adhered together in parallel and penetrate through holes in the shell so as to be arranged on the shell in a sealing manner; the end faces, which are positioned in the shell, of the N optical fibers are aligned; the single output optical fiber penetrates through the hole in the shell so as to be arranged on the shell in a sealing manner, and the optical axis of the output optical fiber is parallel to that of each input optical fiber; the end part, positioned in the shell, of the output optical fiber and the end parts of the N input optical fibers are aligned and lean against together; the matching liquid is arranged in a region, where the end parts of the input optical fibers and the end part of the output optical fiber are positioned, in the shell; the matching liquid exchange device is filled with the matching liquid, is positioned outside the shell and exchanges the matching liquid in the shell through a hole, close to the matching liquid arrangement region, in the shell. The coupling efficiency of the high-power optical fiber power beam combiner provided by the invention is improved, and the manufacturing cost is reduced; the competitiveness of a high-power optical fiber laser device to other laser devices can be improved.