The　liquid　crystal　spatial　light　modulator　is　becoming　a　more　and　more　important　device　due　to　its　wide　applications.　During　its　characterization,　the　phase　modulation　is　the　most　important　one.　In　this　paper,　the　modulation　characterization　of　a　PLUTO　phase-only　spatial　light　modulator　based　on　liquid　crystal　on　silicon　(LCOS)　is　studied　by　applying　the　lensless　Fourier　transform　digital　holography.　In　the　digital　holography,　the　LCOS　is　used　as　a　reflected　sample　which　modulates　the　phase　of　the　incident　wavefront　with　respect　to　the　addressed　gray　level　and　gives　the　information　of　entire　active　region.　This　result　is　then　compared　with　the　result　obtained　by　using　conventional　Michelson　Interferometric　method　and　both　results　are　in　good　accordance　with　each　other.　At　last　the　same　holographic　set　up　is　used　for　the　imaging　of　phase　grating　as　a　reflected　object　which　is　addressed　to　the　LCOS　and　the　clear　profilometry　of　the　grating　is　achieved.