Abstract-In this paper, using moment method in the spectral domain, full wave analysis of two orthogonal microstrip transmission lines in two layered PCB board is presented. First, using 1-dimensional spectral domain method, the propagation constants and the currents on each line are obtained, without considering of the other line. Then, using Galerkine's method in 2 dimensional spectral domain, the scattering parameters of the structure are calculated. The results of our analysis are compared by the quasi-TEM approach. Comparisons show good agreement between our results and quasi-TEM approach.