A new potassium ion-selective electrode based on saturated uruahiol crown ether (3, 3'-n-pentadecyldibenzo-30-crown-10) is described. The electrodes exhibited a linear response to the potassium ions within the concentration range 1×10^-6~1×10^-1 M KCl. Their calibration plots had a slope of 58 mV per activity decade at 25℃. The lower limit of linear response was five to ten times lower than valinomyoin and other crown ether type electrodes.