The coupler design for X-band hybrid dielectric-iris- loaded accelerator has been studied. Firstly, the S parameter versus the coupler cavity radius b, the iris aperture w and its thickness h has been simulated by Microwave Studio for the ordinary coupling cavity due to its simplicity. We have obtained the primary experiment result of the standing-wave ratio of the coupling cavity being 1.82. Secondly, the new coupler with the dual symmetric coupling ports , which first converts RF from TE to TM mode in a pure metal section and then a tapered transition section is added for high efficiency transmission to the dielectric accelerator section, has been calculated. The simulated results show that it is capable to convert the rectangular TE10 mode into circular TM01 mode with high efficiency.