Aiming at the miniaturization, integration and inexpensive design requirements of RF microwave system, the high-density vertical interconnection technology of microwave millimeter wave multi-layer board is studied by HFSS software 3D modeling and simulation. The frequency characteristics of different structural parameters are compared, and the transmission performance in some frequency bands is improved by adding interlayer pads. The S11 is less than –20dB in DC~20GHz. Based on the high-efficiency vertical interconnection technology, 3D vertical synthesis of 32-channel input 4-beam output crossover network is realized. Component network volume is only 125mm×30mm×1.8mm, the S21≤–10.95dB, VSWR≤1.4. It’s better to realize the X-band composite output function.