Abstract: Free Electron Laser and high-brightness synchrotron radiation light source, have put forward higher requirements on the performance of the coupler for the linear accelerator. Unfortunately, the traditional coupler due to asymmetric field may induce transverse kick and cause transverse emittance degradation. In this paper, a new type of single feed coupler loaded with dielectric cylindrical rods is introduced. Its structure is very simple. The dipolar and quadrupolar electric field amplitude asymmetry for the new coupler are -0.0794% and -0.066% , but the ones are 5.02% and 2.99% for the traditional coupler, which shows that the new coupler can reduce efficiently the field asymmetry. Furthermore, this paper describes the structural finite element analysis of the accelerator coupler. The structural behaviors such as thermal loss, thermal field, thermal directional deformation and thermal stress are very important. Structural analysis results of the couplers shows the little difference in thermal performance between the traditional coupler and the new coupler. The new coupler may be used to improve performances of light source.