Imaging, feature extraction, and recognition of targets with micromotion by retrieving their three-dimensional micromotion trajectories (3-D MMTs) have attracted a lot of interest in recent years. We propose a method for retrieving the 3-D MMT of a rotating target based on the interferometric phases obtained using a wideband interferometric radar system with three antennas positioned in L-shape. First, the micro-Doppler effect of rotating target is theoretically analyzed with formulas derived. Then, the instantaneous frequencies are extracted via the short-time Fourier transform and the Viterbi algorithm. The echo signals received by these three antennas are decomposed by the intrinsic chirp component decomposition method, and the interferometric phases of different scatterers are respectively obtained. Finally, the 3-D MMTs of rotating target are reconstructed by exploring the interferometric phases and the range-slow-time data. The effectiveness of the proposed method is validated by both simulations and practical experiment using a Ka-band interferometric radar.