Abstract: A Baum-Liu-Tesche(BLT)equation based approach is presented for the fast prediction of electromagnetic wave coupling with the transmission lines (TL)penetrating through a metallic enclosure. After the decomposition of the whole problem according to the electromagnetic topology theory, the transfer function at the specific node of field coupling to TL is obtained according to Agrawal model. Consequently, the induced current on the termination loads inside the enclosure can be calculated using the generalized BLT-equation.The proposed method is employed to predict the induced current on loads of a single penetrating conductor, multiple penetrating conductors and TL network, and results are in agreement with those calculated using the full wave analysis.The time consumption of the proposed method is about 1/10 000 as much as that of the full wave analysis method, and the memory is reduced by dozens of times compared with the full wave analysis method.