Abstract:The reduction mechanism of metal chloride coordination ions is elucidated with elementaland experimental study. Through the elemental study one can know that the galvanostatic stepmethod or chronopotential curves are very convenient to the determination of cathixlic reductionmechanism of metul chlorides. Through the variation of iτ^1/2 with the concentration of Cl^-  the discharging species at the surface of cathode can be determined as well as the rcaction mechanism, cuprous chloride , zinc chloride and lead chloride are used as examples to illustrate the ele-mental study. Their reaction mechanism can be expressed as:
( 1 ) CuCl₃^2- →CuCl₂^- +Cl^- is a fast preceding reaction , and CuCI₂^-+e→Cu+2 Cl^- is adischarging reaction with mass transfer determined step.
(2) ZnCl₃^- →ZnCl₂+ Cl^- is a fast preceding reaction , and ZnCl₂ + 2e→Zn + 2Cl^-, onestep discharging with diffusion controlling step.
( 3)PbCl₄^2-+ 2e →Pb+4Cl^-and )PbCl₃^-+ 2e →Pb+3Cl^-  there is no preceding reactioninvolved in the lead chloride case and the direct discharging step is also controlled by the diffu-sion step.

Key words: cathodic reduction metal chloride coordination ions copper chloride zinc chlo-ride lead chloride chronopotential method