Abstract: An inner braced and nested assembly manipulator configuration which can realize dual passive compliance is proposed in order to solve the problems that fragile workpieces are prone to break, when the manipulator is used to grasp and assemble thin-walled fragile workpieces, because of appearance inaccuracies of the workpieces. Firstly, the operating procedure for the manipulator gripping thin-walled fragile raw material ring for diamond synthesis is described, and potential assembly process faults are analyzed, and some standards are put forward for designing the structure of dual passive compliant manipulator. The design processes for key compliant ring of the manipulator are described. Secondly, a three-dimensional model of the manipulator is created and imported in ADAMS for simulation analysis in order to study the response of the manipulator, and the stresses on the workpiece as well as the force and deformation of the compliant ring during assembly are acquired. The simulation results demonstrate that the designed manipulator structure can adjust its position and posture for grasping the workpiece through adaptive deformation, to successfully finish the assembly even when there are position and posture deviations between the thin-walled fragile workpiece and the punch to be assembled. Finally, the correctness of the research results is proved by designing and manufacturing the corresponding manipulator prototype to carry out the actual assembly experiment.