The kinematic design of a medical parallel manipulator used for chest compressions in the process of cardiopulmonary resuscitation (CPR) is presented in this paper. According to the requirements of CPR action from medical viewpoints, a 3-PRS (prismatic-revolute-spherical) parallel manipulator (PM) is designed utilizing an architectural optimization methodology for such applications. The dynamic modeling is performed for the 3-PRS PM by two different approaches of Lagrangian formulation and virtual work principle utilizing a simplification hypothesis. Simulation results verify the accuracy of the derived dynamic equations quantitatively, and demonstrate the rationality of the adopted simplified hypothesis. The research work presented here provides a sound base to develop a new medical manipulator to assist in CPR operation, which is expected to reduce the workload of doctors in rescuing patients significantly.