Abstract: This paper proposes a novel broadband three-dimensional polarization-rotating surface, which utilizes a slotline-microstrip-slotline coupling scheme to achieve a 90° polarization rotation over a wide frequency band. To enhance design efficiency, a transmission-line type equivalent circuit model is developed, and the Chebyshev function is employed to synthesize the equivalent circuit model. Using this synthesis method, the equivalent circuit parameters can be directly determined based on the specified relative bandwidth and return loss. As an example, a fourth-order polarization-rotating surface with a relative bandwidth of 80% and a return loss of 10 dB is designed. The mapping relationship between the equivalent circuit model and the physical parameters of the structure is established to facilitate fast modeling of the unit cell. Finally, the designed three-dimensional polarization-rotating surface is fabricated and measured, and the measured results show good agreement with the simulation results. In contrast to the conventional polarization-rotating surface, the proposed three-dimensional polarization-rotating surface possesses both wideband transmission characteristic and angular stability.