Abstract: A new and sensitive polarographic wave caused by Cu(Ⅱ) amoxicillinum complex in 0.2 mol/L NH₃·H₂O NH₄Cl(pH=9.00) medium has been investigated. The polargraphic wave is characterized by an adsorptive reduction wave and the peak potential is about-0.805 V (vs.SCE). The peak height is linear with amoxicillinum concentration over a range of 3.0×10^-7 to 8.0×10^-5 mol/L,and the detection limit is 2×10^-7 mol/L. The method has been developed for the determination of amoxicillinum in capsules.