Layered　2D　transition　metal　dichalcogenides　(TMDCs)　exhibited　fascinating　nonlinear　optical　(NLO)　properties　for　constructing　varied　promising　optoelectronics.　However,　exploring　the　desired　2D　materials　with　both　superior　nonlinear　absorption　and　ultrafast　response　in　broadband　spectra　remain　the　key　challenges　to　harvest　their　greatest　potential.　Here,　based　on　synthesizing　2D　PdSe2　films　with　the　controlled　layer　number,　the　authors　systematically　demonstrated　the　broadband　giant　NLO　performance　and　ultrafast　excited　carrier　dynamics　of　this　emerging　material　under　femtosecond　visible-to-near-infrared　laser-pulse　excitation　(400-1550　nm).　Layer-dependent　and　wavelength-dependent　evolution　of　optical　bandgap,　nonlinear　absorption,　and　photocarrier　dynamics　in　the　obtained　2D　PdSe2　are　clearly　revealed.　Specially,　the　transition　from　semiconducting　to　semimetallic　PdSe2　induced　dramatic　changes　of　their　interband　absorption-relaxation　process.　This　work　makes　2D　PdSe2　more　competitive　for　future　ultrafast　photonics　and　also　opens　up　a　new　avenue　for　the　optical　performance　optimization　of　various　2D　materials　by　rational　design　of　these　materials.