Abstract: An accurate and efficient multi-domain analysis approach is presented for radiation characteristic analysis of radome-enclosed large slotted-waveguide antenna arrays based on parallel domain decomposition algorithm(DDA) finite element-boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA). Each slotted-waveguide antenna and the radome are taken as sub-domains by employing the finite element method(FEM) based on the regional entities, and the sub-domains communicate through the boundary integral (BI) equation. In the radome FEM domain, the DDA can be applied to the FE-BI-MLFMA to greatly reduce the computation resource and achieve high efficiency. The comparisons of the numerical results with the conventional single-domain FE-BI-MLFMA demonstrate that the multi-domain method has good accuracy and high efficiency. The frequency-domain radiation characteristics of the large slotted-waveguide antenna arrays with radome are calculated and studied.