Abstract: A method for analyzing waveguide slots array is investigated. The finite element-boundary integral (FE-BI) method is introduced to calculate waveguide slots array antennas. The numerical model based on FE-BI is established. Then by obtaining the equivalent magnetic current on the surfaces of the slots,far field radiation characteristics of the waveguide slots array can be acquired. Also simulated and measured results are compared to verify the efficiency and accuracy of the presented method. The good agreement shows that FE-BI can be utilized as an efficient method for analyzing waveguide slots array.