Based on electrical-mechanical analogies, a principle of vibration isolation was presented, and a new vehicle suspension employing inerter, which can ease conflicts among individual performance measures for conventional suspension and improve on passenger comfort, was designed. After a quarter-car model was established, parameters of the suspension were optimized, and performance benefits in the suspension were also analyzed in comparison with a conventional suspension by application of mechanical impedance in the frequency domain. The results of simulation show that passenger comfort is remarkably improved on the suspension employing inerter without dynamic tire load and suspension working space rising. It laid the theoretical foundation for engineering application of the suspension employing inerter.