Abstract: A PVC-membrane lidocaine-selective electrode based on tetra-mchlorophenyl borate is described. The effect of plasticizers on the electrode characteristics was studied and dinonylphthalate was recommended as the best solvent mediator for the preparation of electrode. The linear response range of the electrode was shown to be 6.3×10^-6～1.0×10^-1mol/L with a slope of 59.5 mV/pC and a detection limit of 1.1×10^-6 mol/L. The optimum working pH range is 2.7～6.1. The correlation between the potentiometrie selectivity coefficients and the molecular connectivities of varoious drugs was discussed.