This paper proposes compact and wideband crossover and monopulse comparator based on the new multi-layer vertical transition of substrate integrated waveguide (SIW). Through etching slot lines in the internal layers and arranging vias to connect the top and bottom layers of the stacked SIW, the transition structure can excite the TE-like mode and stacked TE-like mode, simultaneously. By properly designing the physical size of the transition, good transmission and isolation characteristics of the dual-layer SIW crossover and quad-layer monopulse comparator are readily achieved. Finally, two samples are fabricated for demonstration. The bandwidth and size of the proposed crossover are 28.6% and 10.5λ, and that of the comparator are 20% and 12.05λ, respectively. Compared with the conventional prototypes, the bandwidths of proposed ones increased by nearly 50% at comparable dimensions, especially the comparator, which has tremendous potential utilization value in multi-port multilayer SIW beamforming networks and radar tracking systems.