Magnetorheological elastomer (MRE) actuator is the core component of smart vibration isolation application system, and its structure optimization is the key to determining the upper limit of actuator's performance and the effectiveness of system's control. However, there have been few optimization methods and theoretical research on MRE actuators. In this paper, a new joint parameter optimization method of an MRE actuator is proposed based on its mechanical structure and effective magnetic circuit, with the optimization goals of superior magnetic-control performance, low power consumption and fast response time. Firstly, with the effective combination of genetic optimization algorithm and electromagnetic finite element analysis method, the optimization programming of MRE actuator is completed based on the joint simulation of MATLAB and COMSOL. Secondly, the optimization design of global size structure of the actuator is realized with the advantages of superior magnetic-control performance (526.21 mT), low power consumption (44.05 W) and fast response (5.43 ms). Lastly, the MRE actuator assembled after optimization is tested by a test system, verifying the feasibility and effectiveness of the proposed optimization method. The proposed joint optimization method is not only suitable for the structure of MRE actuator in this paper, but also can provide theoretical reference for the optimization design of common MRE devices in multi-field vibration reduction/isolation applications.