Helicity-dependent　photocurrent　(HDPC)　of　the　surface　states　in　a　high-quality　topological　insulator　(Bi0.7Sb0.3)2Te3　nanoplate　grown　by　chemical　vapor　deposition　(CVD)　is　investigated.　By　investigating　the　angle-dependent　HDPC,　it　is　found　that　the　HDPC　is　mainly　contributed　by　the　circular　photogalvanic　effect　(CPGE)　current　when　the　incident　plane　is　perpendicular　to　the　connection　of　the　two　contacts,　whereas　the　circular　photon　drag　effect　(CPDE)　dominates　the　HDPC　when　the　incident　plane　is　parallel　to　the　connection　of　the　two　contacts.　In　addition,　the　CPGE　of　the　(Bi0.7Sb0.3)2Te3　nanoplate　is　regulated　by　temperature,　light　power,　excitation　wavelength,　the　source–drain　and　ionic　liquid　top-gate　voltages,　and　the　regulation　mechanisms　are　discussed.　It　is　demonstrated　that　(Bi0.7Sb0.3)2Te3　nanoplates　may　provide　a　good　platform　for　novel　opto-spintronics　devices.