Abstract: Based on the sinusoidal motion error model of airborne synthetic aperture radar (SAR), the motion compensation (MoCo) methods for airborne ultrawide band (UWB SAR) are studied. First, we explain the rationale of the two-step MoCo strategy. And an analysis of the advantage and disadvantage of this MoCo strategy is carried out. Based on the analysis results, an extended two-step MoCo strategy with modified implementation flow is proposed, which is called the one-step MoCo strategy. In one-step MoCo strategy, the second-order MoCo used for compensating the range-variant phase error is implemented before the range cell migration correction (RCMC) processing, instead of after the RCMC processing. As compared to the traditional two-step MoCo strategy, the one-step MoCo strategy has better performance on compensating the high frequency motion error. This paper deducts the proposed MoCo method in detail, and proves its validity with simulation experiment.