In this paper, we consider a floating raft isolation system with elastic limiters. The limiters might be "contact" or "no contact", thus forming a unilateral system generating possible contacts. In order to avoid the large displacement of the floating raft under shock, limiters might be adopted but good limiters design requires the values of the gaps. Based on the contact dynamics, the multi-degree-freedom dynamic model of floating raft isolation system with elastic limiters is established. The artificial neural network has been developed to dingtinguish the contact state of elastic limiters at each step. The example analysis shows that the algorithm of neural network for contact can shorten the time of caclaution. From the example analysis, we get some interesting results that may be useful to the ship engineering. © 2011 Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg.