Abstract: The common electrochemical techniques for determination of trace selenium (Ⅳ) are the stripping voltametry and the one making use of polaro-graphic catalytic wave. We combined this two techniques and established a novel method, cathodic stripping catalytic polarography, for the determination of trace selenium. The various experimental conditions and their influence on the results were studied. The method was applied to the ana-lyisis of some practical samples. By using of a Model 883 polarograph with a rotation glass carbon electrode, after enrichment by electrolysis for 3-5 minutes a concentration in the range of 4×10^-9-1×10^-7M selenium could be determined or after enrichment for 20-30 minutes a detection limit of 7×10^-10M selenium was reached. The oxygen in the system was unnecessary to be removed. The electrode process during the stripping catalysis of selenium was also studied with the combination of glass carbon electrode and a bulk mercury. The reaction mechanism involved in this process was discussed.