Abstract: In this work,the adsorptive stripping behaviour of trace cysteine on mercury-film electrode in the presence of copper (I) have been studied and the mechanism is discussed.The process of electric accumulation is considered that chemical reaction is previour to the adsorption.With Britton-Robinson solution (pH3.0) as medium,a sharp sensitive peak has been observed,and the cysteine concentration over the range of 1.0×10^-10-9.0×10^-10Mis in good linear relationship with the stripping peak current values.The detection limit is as low as 5.0×10^-11M