The molecular structure of CL-20 synthesized by authors has been identified by FTIR, ¹HNMR,¹³CNMR,CIMS.UV and elemental analysis. The four polymorphs(α,β,γ and ε)of CL-20 was prepared,and they were characterized by FTIR.The characteristic peaks of the polymorphs in the“fingerprint”region(1200～700cm^-1)are in agreement with those reported in literatures. The results show that the structureof CL-20 and its four polymorphs the authors synthesized are undoubted and in high purity.