The structure and size of U. S. strategic missile are introduced. Modernization plans for the triad of strategic nuclear forces are analyzed. The development trend of U. S strategic missile is studied.Finally,the deployment of U. S. strategic missile is forecast from 2020 to 2045. It is concluded that U. S. will modernize strategic missiles and associated infrastructure for customized deterrence with excellent operational adaptability. The new generation strategic missiles will finish deployment until 2045.