Abstract: The stability constants of coordition compounds of 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6) and dicyclohexyl-18-crown-6 (DCH18C6) with lanthanide (Ⅲ) are determined. The results show that for lighter lanthanides the stability constants of coordination compounds of 18C6 and DCH18C6 decrease with an increase of atomic number, and the coordinating ability of the crown etheres decreases in the order 18C6>DCH18C6> DB18C6. For DB18C6, weak coordination compounds are formed with heavier lanthanides, but none are formed with lighter lanthanides.