Abstract: A low computational complexity wideband beamforming synthesis method is proposed based on the time-domain structure. Firstly, the concept of adaptive nulling beamforming design is introduced, which achieves precise control of the array response in the sidelobe region by setting virtual interference sources at specific frequencies and angles and iteratively adjusting the control parameters to meet the design requirements. Secondly, the proposed method allows for flexible adjustments based on the existing beampattern design, enabling rapid updates for the beampattern according to changes in design parameters such as sidelobe level. Theoretical studies illustrate that compared to existing beampattern synthesis methods based on interior point algorithms, the proposed method reduces the computational complexity of each iteration, effectively improving efficiency in broadband beampattern synthesis. Simulation and experimental results in a semi-anechoic chamber demonstrate that the beamformer designed by the proposed method exhibits lower sidelobe levels and superior suppression of directional interference compared to conventional fixed beamformers.