This paper presents the design and analysis of a new micro-gripper with a constant force mechanism (CFM). The device in this design contains two modules: constant force mechanism module and gripper module. Details of this modular design has been discussed. The constant force output of the CFM module is achieved by the bistable beam mechanism. The gripper module is actuated by one piezoelectric stack actuator which can provide high resolution for the output displacement. Amplifying mechanism is used in the gripper module to enhance the motion performance. FEA simulation is carried out to verify the design. A prototype of the gripper device has been fabricated and tested. Experimental results verify the performance of the developed gripper.