In this work, a polarization rotating surface is designed and analyzed and applied to the decoupling of ultra-wideband antennas. A method of using dual-size combined rings is proposed to expand the operating bandwidth to 4.8GHz–18.2GHz, and the polarization conversion rate within the entire bandwidth is higher than 99%. Based on the principle of polarization mismatch, placing the polarization rotating surface between ultra-wideband antennas for decoupling can reduce the coupling between antennas by an average of 20dB within the operating bandwidth. Simulation and experimental results consistently prove its excellent decoupling capabilities and ultra-wide operating bandwidth.