A quantitative nuclear magnetic resonance(qNMR) method was established for the determination of the organic impurities contents in the reference material hexanitrohexaazaisowurtzitane(CL-20).The main impurities in the reference material were confirmed to be ethyl acetate and monoacetylpentanitrohexaazais-owurtzitane(MPIW) by analyzing the NMR spectrum.Hexamethyldisiloxane in CCl4 solution with its NMR peak of δ 0.06 was selected as the internal standard which was added into the CL-20 in acetone-d6 solution without tetramethylsilane(TMS).After investigating the effect of delay time (D1) and number of sampling(NS) on quantitative NMR experiments,the experimental parameters were chosen with D1 of 20 s and NS of 32.Using the optimized experiment parameters,it was found that the contents of ethyl acetate and MPIW were 0.035 16% and 0.156 2%,with RSDs of 0.91% and 0.86%,respectively.