Miniaturization has increasingly become a crucial prerequisite in various magnetorheological (MR) drive application scenarios. Owing to their high controllability and low response time, MR rotary actuators are developed for numerous feasible actuation solutions. However, the incident low degradation efficiency in the miniaturization limits the application of MR rotary actuators. In addition to torque capacity, structural simplification and easy machinability are also essential for miniaturization. In this study, a novel lamellar excitation structure (LES), which is interleaved with induction coils and ring-shaped iron cores, is proposed to improve the comprehensive performance of a miniature MR rotary actuator. The optimisation of the magnetic field distribution is realised by adopting an equivalent magnetic modelling method. The miniature MR actuator is incorporated into a turbine generator to evaluate the torque capability of the proposed LES-incorporated MR actuator via a kinematic model of the rotating shaft. The LES-incorporated MR rotary actuator demonstrates more favourable deceleration efficiency and torque capacity than conventional MR rotary actuators. The speed reduction per unit power Δn/P can be increased by 500% at most. The torque enhancement ratio-to-volume ratio (TEVR) value of LES is approximately 80 times higher than that of other optimised structures. We believe that this study is significant in improving the comprehensive performance of miniature MR rotary actuators, expanding the applications of MR actuators in miniaturised scenarios.