A novel large phase-delay transmission line based on dual printed circuit boards (PCBs) for substrate integrated waveguide (SIW) is proposed. Rectangular slots and metallic vias are used to enhance the phase delay feature. The simulated results show the phase difference of the proposed phase-delayed SIW with dual PCBs is -577 degrees at the concerned frequency of 12 GHz. The phase-delay characteristic of proposed design has been analyzed through simulations compared with both micro-strip line and single-layer SIW which using the same definite physical length. The simulated results show that phase-delay performance of our design is far superior to that of the traditional microstrip or the single-layer SIW.