Developing　novel　optical　materials　with　large　and　ultrafast　nonlinear　optical　(NLO)　response　is　significant　for　photonics　and　optoelectronics.　Cuprates　as　the　representative　one-dimensional　(1D)　strongly　correlated　material　show　promising　NLO　properties,　but　relevant　research　is　quite　rare.　Here,　using　Ca2CuO3　nanosheets　as　the　prototype,　we　systematically　explored　the　NLO　performance　and　ultrafast　carrier　dynamics　of　these　cuprate　nanosheets　prepared　by　a　ball-milling　process.　The　obtained　Ca2CuO3　nanosheets　exhibited　convertible　NLO　behavior　from　saturable　absorption　(SA)　to　reverse　saturable　absorption　(RSA)　with　strong　absorption　coefficient,　induced　by　increasing　wavelengths　and　duration　of　excitation　pulse.　In　addition,　we　revealed　their　ultrashort　relaxation　time　in　(sub-)picosecond　scale　for　photogenerated　carriers,　mainly　owing　to　the　midgap　state-assisted　recombination　by　emitting　multiple　phonons　and　spinons.　Furthermore,　the　similar　NLO　feature　also　investigated　in　isostructural　Sr2CuO3　and　Ba2CuO3　nanosheets　further　indicated　the　excellent　NLO　performance　of　1D　strongly　correlated　cuprates.　This　work　opens　up　a　new　avenue　for　future　photonics　with　1D　strongly　correlated　materials　as　the　novel　platforms.