Abstract: To address the problem that limited angular resolution in limited-element millimeter-wave radar causes spatial phase coupling and failure of independent displacement estimation when monitoring angularly adjacent targets at equal range, a millimeter-wave radar displacement monitoring method for angularly adjacent targets is proposed. The proposed method first obtains a coarse range-angle map through two-dimensional fast Fourier transform (2D-FFT) and selects the target range bin. Then, an improved diagonal-loading iterative adaptive approach (MDL-IAA) is applied to the selected range bin for super-resolution angle estimation and fixed angular support set acquisition. Finally, under the constraint of the fixed angular support, a joint spatial decoupling operator is constructed to linearly project the original array snapshots, enabling independent complex signal reconstruction for each target and subsequent displacement estimation. Simulation and experimental results show that, when the angular separation between targets is approximately two-thirds of the array angular resolution, the proposed method can still achieve sub-millimeter-level independent displacement monitoring, which validates the effectiveness of the proposed method.