Beam-guiding system (BGS) has two functions, one shifts the array arrangement of the main laser to the spherical irradiation structure which meets the requirements of shooting laser, the other ensures that all the laser beams transmit to the target chamber center with the same light path length. Main issues are focused on the transmission models of the main lasers and shooting lasers and the switch manner between them. Combining the symmetric properties of the beam port distribution on the target chamber, the transmission sub-unit is proposed to simplify the system arrangement. Firstly, considering the quantity and style of the total mirrors and the space size of the target area, the specific transmission models in a transmission sub-unit and the symmetrical division of target area are determined. Then, two possible transmission models for main lasers and shooting lasers are obtained with the constraints of laser polarization and no intersection among beams during propagation. The switch manner is calculated with a stratified baseline algorithm and the relationship between the image and object of the propagation lasers. In this manner, the entire BGS geometric arrangement is figured out.