The micro-Doppler (m-D) features and extracting method based on the FMCW-ISAR is mainly studied in the paper. The target's continuous moving in pulse repetition interval (PRI) will induce the main lobe widening and deviation of the range profile in FMCW-ISAR system. The induced error will influence the processing of the extraction of m-D features and imaging. The accurate micro motion features cannot be obtained by immediately utilizing existing method of extracting m-D features. To solve this problem, the detailed manifestation and characteristics of target's m-D in FMCW-ISAR is analysed firstly. And then, combining with the extended Hough transform, an extracting method of m-D features parameters in FMCW-ISAR based on Polynomial Phase Transform is proposed in the paper. Finally, some results are given for validating the theoretical derivation and the effectiveness of the proposed method