To resolve the tough issue of strong vibration of the secondary suspension system of the heavy construction machinery cab, a novel liquid-filled isolator is designed. Considering the flow-solid coupling effect between liquid and rubber element, a new parallel combination model with nonlinear coupling relationship is proposed, and the influences of different structural parameters on the amplitude-frequency characteristics and the absolute displacement transmissibility of the suspension system are studied respectively. The low frequency dynamic characteristics of the liquid-filled isolator are investigated and analyzed experimentally. The results show that the transmissibility curves for the measured system keep good agreement with the analytical solutions of the nonlinear dynamics equation, which verifies the validity of the mathematical model. Moreover, the results in the random test show that the novel liquid-filled isolator has obvious vibration isolation effect in both low and high frequency bands, especially the amplitude’s decay rate at high frequency also reaches nearly 90%. This study provides meaningful reference value for the optimized design of the future novel liquid-filled isolator.