Since there is little study on subsystem parameters design for powerpack two-stage isolation system attached with a subsystem, experimental method was adopted to tackle the situation. Effects of subsystem parameters (isolator general stiffness, isolator damp, isolator stiffness ratio) on vibration isolation performance and dynamic characteristics of a certain diesel multiple unit powerpack two-stage vibration isolation system were studied. The results showed that the powerpack two-stage vibration isolation system had excellent vibration isolation performance in both conventional condition and shutdown condition of engine when the subsystem act as a vibration absorber of the main system. And a better vibration isolation performance can be obtained with proper value of the stiffness of subsystem isolators,damping and stiffness ratio.