Optical　helicity　provides　us　with　an　effective　means　to　control　the　helicity-dependent　photocurrent　in　the　spin-momentum-locked　surface　states　of　topological　insulators(TIs).Also,the　TIs　show　potential　in　polarization　de-tection　as　an　intrinsic　solid-state　optical　chirality　detector　for　easier　integration　and　fabrication.However,the　com-plex　photoresponses　with　the　circular　photogalvanic　effect,the　linear　photogalvanic　effect,and　the　photon　drag　effect　in　the　TIs　prevent　them　from　direct　chirality　detection　of　the　elliptically　polarized　light.Here,by　fitting　with　the　theoretical　models　to　the　measured　photocurrents,the　microscopic　origin　of　different　components　of　the　helicity-dependent　photocurrent　has　been　demonstrated.We　show　a　comprehensive　study　of　the　helicity-dependent　photocurrent　in(Bi1-xSbx)2Te3　thin　films　of　different　thicknesses　as　a　function　of　the　light　incident　angle　and　the　gate-tuned　chemical　potential.The　observation　of　the　light　incident　angle　dependence　of　the　helicity-dependent　photocurrent　provides　us　with　a　polarization　detection　strategy　using　a　TI　thin　film　without　the　use　of　any　additional　optical　elements,and　the　detection　accuracy　can　be　enhanced　by　gate　tuning.Additionally,the　Stokes　parameters　can　be　extracted　by　arithmetic　operation　of　photocurrents　measured　with　different　incident　angles　and　gating　voltages　for　complete　characterization　of　the　polarization　states　of　a　light　beam.Using　this　means,we　realize　the　polarization　detection　and　the　Stokes　parameters　analysis　with　a　single　device.Our　work　provides　an　alter-native　solution　to　develop　miniaturized　intrinsic　polarization-sensitive　photodetectors.