epsilon-HNIW was prepared by a one-pot method in concentrated nitric acid from tetraacetyldiformylhexaazaisowurtzitan e (TADFIW). gamma-HNIW was firstly obtained, then gamma-HNIW was directly transformed to E-HNIW in the solution in which nitration reaction occurred. The acid number of E-HNIW prepared by the method mentioned above is less than 0.2%, yield of E-HNIW is up to 91%, and the purity of e-HNIW is up to 99.5%. Because steps of filtration and drying of gamma-HNIW were omitted, the process by which E-HNIW was prepared simplified greatly.