Under engine idling condition， the mechanism of rattle between damping spring and secondary side and the rattle between secondary side spline and transmission input shaft when dual mass flywheel matched with dual clutch transmission were studied. The knocking energy was proposed as an index to evaluate the rattle noise. The design of experiments （DOE） method was used to guide the simulation， and the influences of the key parameters of the dual mass flywheel on the impact energy were clarified. The solution of optimize basic friction to restrain rattle were proposed. The effectiveness of DOE simulation test was verified by experiments， and the consistency between the proposed impact energy evaluation method and subjective evaluation results was verified.