The　azimuth　deviation　on　tooth　flanks　is　a　significant　factor　in　transmission　performances　for　helical　gears.　A　simulating　investigation　is　performed　using　the　TCA　(Tooth　Contact　Analysis)　technique　for　the　kinematic　effects　on　the　helical　gears　with　azimuth　errors　based　on　ISO-GPS　(Geometrical　Product　Specification)　standard.　In　this　work,　firstly,　the　parabolic　modification　of　a　tooth　surface　for　the　design　model　is　established;　secondly,　the　homogeneous　coordinate　transformation　matrix　is　employed　for　the　azimuth　deviation　modeling　based　on　the　space　rigid　body　kinematics　method;　and　thirdly,　the　influence　of　the　azimuth　deviations　on　the　transmission　performance　is　studied　with　the　tooth　contact　analysis　technology.　©　2017　Taylor　&　Francis　Group,　London.