We propose a simultaneous multi-object micro-displacement measurement method by multi-spectral-peak radar interferometry (MPI). Range-velocity spectrum obtained by a frequency modulated continuous wave (FMCW) radar identifies the range of multiple objects. Micro-displacement of each object is calculated based on the phase shift corresponding to each identified range by interferometry. Therefore, simultaneous micro-displacement measurement for multiple object recognition is achieved. Through evaluations using simulated and measured data, it is shown that the proposed MPI can simultaneously measure micro-displacement characteristics of multiple objects, i.e. a standing human and an idling car. The demonstrated results suggest possibilities of target recognition for traffic safety.