A　functionalized　nanocrystal　cellulose　bearing　amino　and　sulfonic　acid　groups　(Am-sNCC)　is　prepared　through　a　two-step　chemical　modification　of　microcrystal　cellulose　powders,　first　by　sulfonic　acid　and　then　by　a　3-trimethoxysilyl　propyl　ethylenediamine.　The　structure　of　Am-sNCC　is　characterized　by　Fourier　Transform　infrared　spectroscopy　(FT-IR),　X-ray　photoelectron　spectroscopy　(XPS),　and　X-ray　diffraction　(XRD).　A　sulfonated　poly　(ether　ether　ketone　ketone)　(Ph-SPEEKK)　is　synthesized　via　the　direct　sulfonation　of　a　high-molecular-weight　phenylated　polymeric　precursor　under　a　mild　reaction　condition.　The　nanocomposite　membranes　composed　of　the　Ph-SPEEKK　matrix　and　the　Am-NCC　additive　are　successfully　prepared　by　a　solution　casting　method.　The　properties　related　to　their　application　for　proton　exchange　membranes　are　carefully　evaluated.　The　nanocomposite　membranes　containing　Am-sNCC,　which　served　as　a　performance-enhancing　component　to　form　hydrogen　bonding　networks　with　the　Ph-SPEEKK　matrix,　exhibited　much　improved　dimensional　stability,　higher　water　absorption　capacities,　higher　proton　conductivity,　better　mechanical　and　fuel　cell　properties　than　the　Ph-SPEEKK　membrane.