Abstract: Time-modulated array (TMA) can generate harmonic multibeam pointing to different directions while the amplitude of each beam is inconsistent and inefficient. A method to realize low-cost and high-efficiency time-modulated multibeam based on stepped waveform is proposed in this paper. The frequency spectrum and waveform in time domain of TMA is obtain first according to the requirement of multibeam. Then, the stepped waveform is designed to fit the theoretical waveform based on the hardware characteristic of digital attenuators and 0/π phase shifters. By optimization of stepped waveform, the power of undesired sidebands and the ripple of operating sidebands are suppressed, which realizes stable and efficient multibeam scanning. In this paper, an 8-element TMA is proposed to realize five harmonic beams scanning (fundamental and ±1st, ±2nd sidebands). The least significant bit (LSB) of digital attenuator and stepped waveform are modified to find the optimal solution. The simulated result shows the sideband level (SBL) is –31.20 dB while the operating sideband ripple is 0.68 dB. The proposed multibeam time-modulated array antenna has the advantages of low cost, high efficiency, good consistency of multibeam and undesired sidebands suppression, which improves the employment of TMA technology in field of multibeam antenna.