In this paper, a hybridization method of moment (MOM) and equivalent edge currents (EECs) is presented to study the electromagnetic (EM) scattering from the slot antennas fed by the waveguides with arbitrary termination. The EECs is applied to calculate the EM scattering of a conducting plane, including the diffraction of edge, while the MOM is used to obtain the fields in the slots and deal with the coupling between them In conjunction with them, the EM scattering of the slot antennas can be evaluated quickly. Several results are presented, demonstrating the applicability of this technique.