The　present　invention　provides　a　shaft　rotational　speed　measurement　device　and　method　based　on　variable　density　sinusoidal　fringe　pattern.　The　device　comprises　a　variable　density　sinusoidal　fringe　pattern　sensor,　　a　high　speed　image　acquisition　and　transmission　module,　　a　computer,　　and　an　image　processing　software　module.　The　method　comprises　the　following　steps　:　　make　the　variable　density　sinusoidal　fringe　pattern　sensor　attached　on　the　circumferential　surface　of　the　measured　shaft,　　the　variable　density　sinusoidal　fringe　pattern　sensor　is　continuously　imaged　and　recorded　by　the　high　speed　image　acquisition　module,　　the　image　transmission　module　transfers　the　fringe　pattern　signal　to　the　computer,　　the　image　processing　software　module　carries　out　Fourier　transform　to　the　fringe　pattern　signal　in　the　same　position　of　each　frame,　　and　corrects　the　peak　frequency　accurately　by　using　the　peak　frequency　correction　method　to　obtain　the　accurate　fringe　pattern　density　information　of　each　frame,　　obtains　the　time　domain　curve　of　the　rotational　angular　velocity　of　the　measured　shaft,　　and　then　calculate　the　rotational　speed　of　the　measured　shaft　through　the　rotational　angular　velocity　and　sampling　frequency.　The　present　invention　can　realize　non-contact　measurement　of　rotational　speed　of　measured　shaft　within　a　certain　speed　range,　　and　the　measuring　device　is　simple,　　the　measuring　method　is　fast　and　accurate.