Abstract: In a borate buffer medium of pH 8.9,a complex was formed between Zn(Ⅱ) and o-phenanthroline,Zn(phen)2,showing a sensitive polarographic wave at the potential of -1.30 V(vs.SCE).The peak current of the polarographic wave kept a linear relationship with the concentration of Zn(Ⅱ) in the range of 40×10-8-2.0×10-6mol·L-1 (r=0.998 6).Detection limit was found to be 2.0×10-8mol·L-1.Behavior and mechanism of the electrochemical reaction of the polarographic peak was investigated using linearsweep polarography.The method has been applied to the determination of zinc in zinc gluconate oral liquor.