New nitrification systems of N₂O₅/HNO₃/ ionic liquids(ILs, quaternary ammonium salts, caprolactams, imidazoles, pyridines) were used to nitrify tetraacetyl hexaazaisowurtzitane(TAIW) to prepare hexanitro-hexaazaisowurtzitane(CL-20), instead of the commonly used concentrated nitric and sulfuric acid in industrial scale, which was seriously harmful to the environment. The effects of the type, dosage and acidity of ILs and reaction time on yield and purity of CL-20 were investigated. Results show that acidity of ILs is positively correlated with catalytic performance and the [Et₃N(CH₂)₄SO₃H][BSO] shows the best catalytic activity. The optimum conditions are as follows: reaction temperature 60-80 ℃, reaction time 7 h, m([Et₃N(CH₂)₄SO₃H][BSO]):m(TAIW):m(N₂O₅):V(HNO₃)=0.5 g:3 g:4 g:15 mL, with the yield and purity of 94.5% and 98.1%, respectively. ILs can be reused five times and barely with significant loss of catalytic activity.