A rubber isolator with an electromagnetic actuator inside is proposed to isolate wideband vibra-tion of heavy machinery. The rubber isolator can support heavy payload and isolate medium-high frequency vibrations while the electromagnetic actuator can suppress low frequency harmonic vi-brations. The hyperelastic model is applied to simulate the rubber isolator and the effects of rub-ber hardness on the characteristics of the isolator are explored. The stiffness and transmissibility are also tested and calculated. To evaluate the performance of the isolator, a theoretical model of four isolators between the elastic foundation and the heavy equipment is established and the transmissibility of the isolators in the system is calculated. The results have demonstrated that modelling of the isolator is effective and the high frequency performance of the isolator is changed by the elastic foundation.