Abstract: In order to study the factors affecting the overall efficiency of the fiber power bundler, a modeling method was used to analyze the optical field distribution at different positions of the power bundler and the effects of the numerical aperture, core diameter and taper length on the transmission efficiency of the fiber power bundler. The results show that, based on the comprehensive consideration of transmission efficiency and beam quality, the transmission efficiency of the power bundler is 97.17%, and M ²=2.15. In addition, the larger the numerical aperture of the input fiber, the higher the transmission efficiency of the bundler. However, when the numerical aperture of the input fiber is between 0.064 and 0.065, the transmission efficiency decreases due to the introduction of higher-order modes with higher losses. By comparing the transmission efficiency of different output optical fiber core diameters, it is found that the transmission efficiency increases with the increase of output optical fiber core diameter and the increase of taper length. However, in some areas, due to the mode coupling effect and energy diffusion, the transmission efficiency decreases with the increase of the taper length. This result is helpful for the manufacture of beam combiner.