Abstract:  Phase-derived velocity measurement (PDVM) can achieve phase level measurement accuracy, thus has a great application prospect in the field of micromotion feature extraction and target recognition. The PDVM method requires high signal-to-noise ratio (SNR), and the keys of PDVM method are accurate phase extraction and resolving phase ambiguity. In this paper, a PDVM method based on range profiles cross correlation (RPCC) under low SNR condition is proposed. Firstly, a wideband linear frequency modulation (LFM) signal echo model of dechirp processing is established. Then, the RPCC results of adjacent frames are derived, and the peak position phases of the RPCC results are analyzed. After that, in order to improve the applicability of PDVM under low SNR conditions, a method is proposed to accumulate the RPCC results along the slow time dimension. This method can re-extract the peak position phases and obtain the coarse estimate of target velocity, which enables to assist in the subsequent phase ambiguity resolving processing. In addition, in order to suppress the influence of noise on the extracted phase, a filter design method based on the phase spectral characteristics is proposed, so as to further improve the accuracy of PDVM. Finally, the validity of the proposed method and its applicability under low SNR are verified by simulation and experiment.