Abstract: The extraction behaviour of thorium (Ⅳ) with some crown ethers in 1,2-dichloro-ethane from nitric acid, hydrochloric and and picric acid aqueous solutions has beenstudied. In nitric acid media, thorium (Ⅳ) orms Th (NO3)4·2L·HNO3 (L——crown ether)extracted complex with Dicyclohexyl-18-crown-6(DC18C6) or Dicyclohexyl-24-crown-8 (DC24C8). The extraction equilibrium constants (K) determined at 25℃ are: Kdc18C6 = 3.98 and KDC24C8=6.30.The infrared spectra of the extracted complexes (Th (NO3)4·2DC18C6·HNO3 and Th (NO3)4 ·2DC24C8·HNO3) have been examined. The specific absorption bands appeared in differential spectra, indicating that direct bonding probably exists between the extracted metal ion and the oxygen donor in the ring of these crown ethers, and the nitrate group acts as a dentate in these extracted complexes.