A　simple　position　control　strategy　in　stages　is　presented　for　the　underactuated　planar　manipulator　with　passive　joints　and　flexible　links.　The　assumed　mode　dynamic　model　is　established　of　a　2R　underactuated　manipulator　with　a　second　flexible　link　and　a　second　passive　joint.　The　dynamic　coupling　characteristics　and　the　controllability　of　this　system　are　analyzed.　The　position　control　strategy　of　this　manipulator　is　investigated　in　stages　based　on　the　switch　of　the　brake　at　the　passive　joint.　And　the　corresponding　algorithms　of　both　the　active　and　passive　joints　are　designed　by　using　the　PID　method.　Finally,　on　the　basis　of　a　self-designed　experimental　setup　of　an　underactuated　planar　manipulator,　the　position　control　of　this　2R　underactuated　planar　flexible　manipulator　is　experimentally　completed.　The　simulative　and　experimental　results　illustrate　that　the　active　and　passive　joints　can　track　the　targets　perfectly　in　respective　stage　and　the　operational　task　of　this　manipulator　can　be　implemented,　which　verify　the　effectiveness　of　the　proposed　method　and　the　correctness　of　the　dynamic　model　of　the　underactuated　flexible　manipulator.　©　2013　Journal　of　Mechanical　Engineering.