High-power asymmetric pump combiner is the key passive optical device of the high-power continuous all-fiber laser. Multiple pump lights are efficiently coupled into the main fiber through the high-power asymmetric pump combiner, so that enough pump powers are provided for the high-power fiber laser. The current coupling theory of the double waveguide directional combiner can′t be directly applied to the study of the high-power asymmetric pump combiner. In order to solve this problem, the incomplete coupling theory of the double waveguide directional combiner was used as the foundation and the asymmetry was used as the feature of the high-power pump combiner. The coupling coefficients equations and the power equations of the high-power asymmetric pump combiner were further derived and the simulation results were also obtained. The conclusions are as follows. The powers of the pump fiber and the main fiber change periodically. When the taper angle of the pump fiber is between 1° and 1.5°, more than 97% coupling efficiency is obtained. The local variation of the coupling length has little effect on the coupling efficiency. The conclusions are instructive for the designs and productions of high-power fiber coupler.