A　hallmark　signature　of　the　three-dimensional　(3D)　topological　insulator　(TI)　is　that　the　spin-momentum　locked　massless　Dirac　fermions　populate　its　surface　states,　where　the　carrier　spins　are　locked　to　their　momentum.　Here,　we　report　on　the　magnetic-field　induced　helicity　dependent　photogalvanic　effect　(MHPGE)　of　3D　TI　thin　films　Bi　2Te　3　or　(Bi　xSb　1　-　x)　2Te　3　of　different　thicknesses　excited　by　near-infrared　(1064　nm)　under　an　in-plane　magnetic　field.　It　is　found　that　the　MHPGE　current　J　c　x　under　the　longitudinal　geometry,　i.e.,　J　c　x　≥　B　x,　is　induced　by　the　Larmor　procession,　while　that　under　the　transverse　geometry,　i.e.,　J　c　x　≥　B　y,　is　mainly　introduced　by　the　hexagonal　warping,　which　can　be　enhanced　by　the　in-plane　magnetic　field.　Our　work　demonstrates　the　possibility　to　tune　the　spin-polarized　photocurrent　of　the　surface　states　in　3D　TIs　via　a　magnetic　field,　which　may　be　utilized　to　design　new　kinds　of　opto-spintronic　devices.　©　2021　Author(s).