The　kinematic　problem　is　an　essential　algorithm　problem　of　the　manipulator　control.　To　improve　the　performance　of　the　robots,　it　has　been　widely　researched　in　robotics.　In　this　paper,　a　general　kinematic　method　for　R-theta　type　manipulator　is　created　using　the　combination　of　screw　theory　and　dual-quaternion,　it　can　be　applied　to　different　type　of　R-theta　robot　with　different　arm　length.　Screw　theory　provides　a　global　geometric　representation　of　the　kinematics　of　manipulator　which　greatly　simplifies　the　analysis　of　the　mechanism　and　can　avoid　the　singularities　due　to　using　local　coordinates.　With　this　method,　the　kinematics　of　the　R-theta　type　manipulator　is　expressed　by　dual-quaternion　representing　the　screw　motion　of　each　joint　of　the　manipulator.　By　dual-quaternion　only　eight　numbers　are　used　to　express　a　screw　motion.　Meanwhile,　the　motion　transformation　by　dual-quaternion　takes　fewer　calculations　than　the　homogenous　matrix.　Thus,　comparing　with　the　traditional　D-H　parameter　method,　this　method　provides　a　compact,　computationally　efficient　algorithm　of　kinematics　of　R-theta　type　wafer　transfer　robot　which　needs　less　storage　space　and　does　not　suffer　from　singularity　problem.