The　industrial　x-ray　Computed　Tomography　(ICT)　is　increasingly　applied　in　the　manufacturing　industry　for　dimensional　quality　control　especially　in　gear　industry　for　the　plastic　small　module　gears.　To　evaluate　the　measured　gear　and　analysing　the　measurement　uncertainty　including　Monte　Carlo　simulations,　it　is　necessary　to　establish　CT　projection　and　reconstruction　image　for　the　measured　gear.　The　mathematical　model　of　the　projected　image　is　established　for　each　part　including　tooth　root,　involute　tooth　body　and　tooth　root　fillet,　and　then　the　end　section　projection　algorithm　is　obtained　by　the　combination.　The　projection　value　of　the　gear　end　section　at　different　rotation　angles　are　simulated　by　MATLAB,　which　is　combined　to　be　a　grayscale　image　of　the　projection　image.　Based　on　the　filtered　back-projection　algorithms,　the　reconstruction　image　is　created,　which　is　binarized　to　get　the　gear　end　section　data.　The　simulation　results　are　verified　to　be　close　to　the　results　by　Geant4.　The　algorithms　proposed　is　significant　to　the　application　of　gear　measurement　in　industrial　CT,　which　is　also　helpful　for　other　applications　for　complex　surface　parts.　©　2025　IOP　Publishing　Ltd.　All　rights,　including　for　text　and　data　mining,　AI　training,　and　similar　technologies,　are　reserved.