Abstract-A novel algorithm is put forward to separate radar target and moving clutter based on a combination of the low-rank matrix optimization (LRMO) and a decision tree. Similar to the moving object detection in the field of automated video analysis, the proposed separation method, which is carried out in the range-Doppler domain, makes use of different motion variation of radar target and clutter in the spectrogram sequence. The technique is very general but the focus of this paper is on narrowband moving clutter suppression in weather radar. The first step in implementing this method is the generation of a rangeDoppler spectrogram sequence. Then, the LRMO is applied to the obtained sequence to divide target and moving clutter into foreground and background. From the foreground sequence which is obtained by solving the LRMO, foreground frequency and spectral width are combined in a decision tree to obtain a filtering mask to mitigate the narrow-band moving clutter and noise. Data collected by a polarimetric Doppler weather radar known as the IRCTR Drizzle Radar (IDRA) are used to validate the performance of the proposed algorithm. Moreover, its effectiveness in removing narrow-band moving clutter is quantitatively assessed through comparisons with another clutter mitigation method.