Because of the rapid increase of complexity and vulnerability of national critical infrastructure which sustains country’s normal running,and in consideration of the national critical infrastructure facing normal invalidation and intently terrorist attack,more and more developed countries pay great attention to the modeling & simulation of their national critical infrastructure.The basic concept of national critical infrastructure was introduced.The necessary and basic theory and method of modeling and simulation were provided. The latest international developments of modeling and simulation,especially in American were illustrated.Several successful application systems in developed countries were presented.At the end,the importance of that our country should start and develop actively the research in this area was expounded.