To　meet　the　increasing　requirements　for　precision　hybrid　machine　tools,　this　paper　presents　a　geometric　error　propagation　model-based　accuracy　synthesis　method　for　parallel　manipulators　(PMs)　with　one　translational　and　two　rotational　(1T2R)　motion　abilities.　A　unified　geometric　error　propagation　model　of　a　family　of　1T2R　PMs　is　established　with　the　first-order　kinematic　perturbation　method.　A　set　of　geometric　error　propagation　intensity　indexes　is　formulated　to　describe　the　geometric　error　propagation　characteristics　in　a　quantitative　manner.　The　equivalent　effects　of　specified　terminal　accuracy　are　derived　to　directly　determine　the　allowable　values　of　all　geometric　source　errors.　Based　on　these,　a　computation　algorithm　is　summarized　for　designating　a　tolerance　allocation　scheme　to　meet　the　specified　terminal　accuracy　of　a　1T2R　PM.　To　demonstrate　the　accuracy　synthesis　method,　a　novel　1T2R　PM　with　a　2UPR-1RPS　(＇R,＇　revolute　joint;　＇U,＇　universal　joint;　＇S,＇　spherical　joint;　＇P,＇　prismatic　actuated　joint)　topology　is　taken　as　an　example　to　allocate　geometric　tolerances　under　the　specified　terminal　accuracy.　Following　the　tolerance　allocation　scheme,　a　laboratory　prototype　of　the　exemplary　PM　is　fabricated　and　further　experimentally　measured.　The　measured　kinematic　results　indicate　that　the　prototype　possesses　an　acceptable　position　error　smaller　than　0.15　mm,　verifying　the　feasibility　of　the　proposed　accuracy　synthesis　method.　Hence,　the　proposed　method　can　be　applied　as　a　forward　tolerance　design　tool　to　reduce　the　design　iterations　and　development　risks　of　low-mobility　parallel　robots.　©　2022　by　ASME.