Inorganic　cesium　lead　halide　perovskite　(CsPbX3,　X　=　Cl,　Br,　I)　is　a　promising　material　for　developing　novel　electronic　and　optoelectronic　devices.　Despite　the　substantial　progress　that　has　been　made　in　the　development　of　large　perovskite　single　crystals,　the　fabrication　of　high-quality　2D　perovskite　single-crystal　films,　especially　perovskite　with　a　low　symmetry,　still　remains　a　challenge.　Herein,　large-scale　orthorhombic　CsPbBr3　single-crystal　thin　films　on　zinc-blende　ZnSe　crystals　are　synthesized　via　vapor-phase　epitaxy.　Structural　characterizations　reveal　a　＂CsPbBr3(110)//ZnSe(100),　CsPbBr3[-110]//ZnSe[001]　and　CsPbBr3[001]//ZnSe[010]＂　heteroepitaxial　relationship　between　the　covering　CsPbBr3　layer　and　the　ZnSe　growth　substrate.　It　is　exciting　that　the　epitaxial　film　presents　an　in-plane　anisotropic　absorption　property　from　350　to　535　nm　and　polarization-dependent　photoluminescence.　Photodetectors　based　on　the　epitaxial　film　exhibit　a　high　photoresponsivity　of　200　A　W-1,　a　large　on/off　current　ratio　exceeding　10(4),　a　fast　photoresponse　time　of　about　20　ms,　and　good　repeatability　at　room　temperature.　Importantly,　a　strong　polarization-dependent　photoresponse　is　also　found　on　the　device　fabricated　using　the　epitaxial　CsPbBr3　film,　making　the　orthorhombic　perovskite　promising　building　blocks　for　optoelectronic　devices　featured　with　anisotropy.