Based on analysis of a vibration isolation system of an bilinear intelligent damping double-deck, the limitation of classic passive vibration isolation technology was solved in case of relatively complex mix input force signal.The method of using variation derivative to find functional drop direction was proposed.The gradient descent method was used to solve the extremum of a functional, and the functional numerical method was used to obtain the optimal damping curve.Due to the strong non-linear characteristics of controlling curve and even existing a non-derivable problem, a pulse function was introduced and a theoretic deduction was performed.The defects that a curve with non-derivable points could not be solved were overcome so that the proposed method was applicable to an bilinear system modeled.The effects of vibration reduction of the new method, a passive damping system and a semi-active skyhook damping system with three mix signals were investigated, such as the mix signal of single-frequency sine and pulse input signal, the mix signal of random and impact input signal, the mix signal of impact and sine excitation signal.The optimal damping vibration isolation with both the mix signal of random and impact input signal and the mix signal of impact and sine excitation signal are all remarkable.The results showed that the optimal semi-active damping control strategy for an bilinear system is the best one of the five control strategies described here, its anti-vibration effect on mix excitations is obvious.The simulation results of the proposed methods applied to bilinear modeling isolation system are satisfied.