Two open-chain crown ethers 2,2'-(ethylenedioxy)bis[(8-quinolyloxymethyl)benzene], (L1), and 2,2'-(ethylenedioxy)bis[(8-quinaldyloxymethyl)benzene], (L2) have been prepared and characterized by using elemental analysis, IR spectra, 1H NMR spectra and positive-ion FAB mass spectra. The extraction of UO22+ and Th4+ by both open-chain crown ethers, L1 and L2 in chloroform as a diluent was studied at 25 °C. Extraction distribution ratios (D) of UO22+ and Th4+ were investigated as a function of pH, lithium picrate concentration, and extractant concentration. Based on the expertimental results, it was found that 1 : 1 complexes were formed involving either UO22+ or Th4+ with L1, and Th4+ with L2. The extractability of L1 for Th4+ is significantly higher than that for UO22+, the extractabilities of L1 and L2 for Th4+ being almost identical. L1 and L2 used here are not feasible for industry because of their relatively low extractabilities for Th4+ at pH<2.0 and for UO22+ at the extraction conditions used in this work.