Abstract: A sensitive reduction peak of 6-mercaptopurine with copper(Ⅱ) complex was found by single-sweep oscillopolarograph in 0.10 mol/L Britton-Robinson medium,The peak potential was at 0.41 V (vs.SCE), The height of second-order derivative wave was linear with the concentration of 6-mercaptopurine over the range of 4×10^-7 to 1×10^-5 mol/L and the detection limit is 3×10^-8 mol/L. The method was developed for the determination of 6-mercaptopurine in medicine and the average recovery was 98.7%. The electrochemical behavious of 6-mercaptopurine with copper(Ⅱ) complex at Hg electrode and its adsorptive properties were also explored.