This paper presents the design, analysis and testing of a novel three-degree-of-freedom (3-DOF) parallel-kinematic constant-force end-effector. The constant-force end-effector enables a safe interaction between the end-effector and contacted object. To obtain the constant-force property without extra fixing support, the symmetrical bistable flexure hinges are adopted. Then, to reduce the constant-force value, a preloading constant-force mechanism is introduced. The parallel-kinematic mechanism based on flexure hinges is constructed to decouple the 3-DOF motion. FEA simulation study is conducted to investigate the constant-force property and the decoupling ratio of the designed mechanism. Moreover, a prototype is fabricated and experimental testing is conducted to verify the performance of the constant-force mechanism.