The authors have been carrying out numerical studies on the effect of a passive nonlinear absorber system containing a strongly nonlinear stiffness and a large virtual mass (NLVM). In this paper, the performance of this proposed absorber system when used for a base isolated building against harmonic ground motion and impulsive excitation is presented. The NLVM system has the following characteristics. (1) A large virtual mass ratio reduces response acceleration. (2) A strongly nonlinear stiffness avoids a resonance phenomenon and reduces response displacement. We have studied STD, LVM, NLVM, TMD and TMD-VM systems ( shown in Fig. 2 ). The NLVM system is a nonlinear system and the others are linear systems. In order to examine the performance of the NLVM system, the shooting method and the numerical continuation technique are used to examine the resonance curves and also to determine their stability while direct time integration is used to examine the transient behavior of the dynamic system. Firstly, we compared the NLVM system with the STD and LVM systems. As the NLVM has strongly nonlinear stiffness, it makes the peak of the main resonance curve lean in the direction of higher frequencies ( shown in Fig. 3(b) ). Although several stable solutions occur at the same frequencies, we can use the lowest stable solution in the case where initial conditions are zero or small. Therefore, we regard point Z ( shown in Fig. 3(b) ) as the prediction indicator of a maximum amplitude ratio. Even if the initial conditions are large, the probability of converge to the upper periodic solution is reduced while the amplitude ratio becomes large. The NLVM system is shown not to require a large amount of damping even for a large mass ratio. In the case of a sweep excitation, we can neglect resonance phenomena, because it is extremely difficult to generate a resonance phenomenon along the upper periodic solution during a sweep excitation. In the case of a impulsive excitation, the LVM system can reduce the acceleration amplitude ratio drastically. Since the NLVM system is based on LVM, the maximum value of the acceleration amplitude ratio is of the same level with STD( h1 = 20% ). However, both NLVM and LVM systems have a lower limit near the Racc = μ1/(1+μ1). For this reason, an extremely large mass ratio is not recommend. Secondly, we compared the NLVM system with the TMD and TMD-VM systems. Both TMD and TMD-VM are linear systems optimized using the Fixed-point theory. The TMD-VM is equivalent to the TMD except that the additional mass is a virtual mass. The TMD-VM system is more effective than the TMD system at any mass ratio. In the case of a impulsive excitation, the amplitude ratio of NLVM system is of the same level with TMD-VM, whose mass ratio is in the range of μ = 0.5 ∼ 1.0. In this case, the NLVM doesnot have an additional damping while the TMD-VM requires a large amount of damping( h0,opt = 12 ∼ 22% ). In conclusion, the newly proposed NLVM system can avoid a resonance phenomenon and reduce structural response quite effectively.