Controlling the contact force on workpieces is a challenging task for industrial deburring operations. To solve this issue, a novel constant force mechanism(CFM) based on the combination of positive and negative sti ness mechanism is proposed by using folding beam and bi-stable beam. Without using any additional sensors and control algorithms, the proposed mechanism can produce a travel range in constant force manner. In this paper, the design concepts, analytical modeling, finite element analysis (FEA) simulation and experimental studies are presented and discussed. Firstly, a novel spatial CFM is proposed and using the pseudo rigid body(PRB) to established the mathematical model of the whole mechanism. Then, the FEA simulation is performed to validate the correctness of theoretical analysis. In addition, to eliminate the force variation, particle swarm optimization (PSO) method is utilized to find optimal architectural parameters solutions of the CFM. Finally, the experimental tests are performed to verify the performance of the designed CFM. The confguration design and parameter optimization can be further applied to the design of other CFM mechanisms for polishing operations.