A method of combining BiConjugate Gradient(BCG) with Fast Fourier Trans-form(FFT) to analyze the radiation of microstrip antenna arrays is presented, where the spatially discrete BCG-FFT for analyzing microstrip structure is used and the del operators on Green’s functions are transferred from the singular kernel to the expansion and testing functions. The resultant equations are solved by using BCG method in which the matrix-vector product is evaluated efficiently with FFT. The calculated patterns are in good agreement with the measured data. A method of combining Bioconjugate Gradient (BCG) with Fast Fourier Transform (FFT) to analyze the radiation of microstrip antenna arrays is presented, where the spatially discrete BCG-FFT for analyzing microstrip structure is used and the del operators on Green’s functions are The resulting equations are solved by using BCG method in which the matrix-vector product is effectively with FFT. The calculated patterns are in good agreement with the measured data.