Traditional elastic actuator is the flexible structure which needed to connected to the output shaft of the brake. Besides, according to the principle of the state of the connection, it could be divided into series elastic actuators (SEA), as well as parallel elastic actuator (PEA) [3]. Therefore, the brake output has a certain flexibility, providing compliance or shock absorption, and other functions. However, since the spring constant is a fixed value, it only could be decided in the design. Namely, it is hard to adjust by following the different user's requirement. Thus, we propose a flexible structure design which driven by electromagnetic force, by varying the magnitude of the electromagnetic force that can actively adjust the stiffness change and improve the flexibility of the traditional spring immutable problem. Then, one of the most important thing is that we do not need the extra mechanism which in order to adjust the stiffness, and even increasing the structural complexity. In other words, in the meanwhile, achieving actuator without real spring (no loss), reducing the size and simplify the structure, high response adjusting in stiffness modulation. Therefore, for the exoskeleton robot for compliance and simplify the size of demand, this research has significant innovative and progressive.