Two-dimensional　(2D)　organic-inorganic　hybrid　perovskites,　benefiting　from　their　natural　anisotropy　of　quantum-well　motifs　and　optical　properties,　have　shown　remarkable　polarization-dependent　responses　superior　to　the　3D　counterparts.　Here,　for　the　first　time,　multiwavelength　polarization-sensitive　detectors　were　fabricated　by　using　single　crystals　of　a　guanidine-based　2D　hybrid　perovskite,　(BA)(2)(GA)Pb2I7　(where　BA(+)　is　n-butylammonium　and　GA(+)　is　guanidium).　Its　unique　2D　quantum-well　structure　results　in　strong　crystallographic-dependence　of　optical　absorption.　Strikingly,　our　crystal-based　photodetector　exhibits　a　prominent　photocurrent　dichroic　ratio　(I-max/I-min)　of　similar　to　2.2　at　520　nm,　higher　than　the　typical　2D　inorganic　materials　(GeSe,　similar　to　1.09,　PdSe2,　similar　to　1.8).　In　addition,　notable　dichroic　ratios　of　1.29　and　1.23　at　405　nm　and　637　nm　are　also　created　for　the　multiwavelength　polarized-light　detection.　The　prominent　detecting　performances,　including　low　dark　current　(1.6x10(-11)　A),　considerable　on/off　ratio　(similar　to　2x10(3)),　high　photodetectivity　(similar　to　3.3x10(11)　Jones)　and　responsivity　(similar　to　12.01　mA　W-1),　make　(BA)(2)(GA)Pb2I7　a　promising　candidate　for　polarized-light　detection.　This　work　sheds　light　on　the　rational　engineering　of　new　2D　hybrid　perovskites　for　the　high-performance　optoelectronic　device　applications.