Abstract: In order to understand and obtain the whole structure RF characteristics of the disk-loaded accelerating tube, the redesigned axis-symmetric coupler was adopted to replace the real 3-D one during the calculation process by ANSYS. Much less computer sources and time were required to simulate the whole structure with only one single PC by taking full advantage of the structure’s axis-symmetric characteristic. The accelerating tube for the BEPC Ⅱ linac was used as an example to validate this method. The ANSYS simulated filling time, attenuation factor and bandwidth are 856 ns, 0.56 Np and 3.55 MHz respectively, while the experimental measured ones are 830 ns, 0.57 Np and 4.7 MHz respectively. It can be seen that the ANSYS simulation and experimental measurement are consistent as a whole, and the simulation can provide very valuable reference for the real design and fabrication.