The present paper is a detailed study on the atomic layer deposition of selenium and antimony on platinum electrode by electrochemical atomic layer epitaxy (EC-ALE). Voltammetry and coulometry experiments were performed in this work to investigate the electrochemical behaviours of selenium and antimony on the polycrystalline platinum electrode. The results show that on Pt substrates Se ions can directly form a UPD layer with full coverage without the formation of bulk Se. The total Faradaic charge of the UPD Se is calculated to be 924 μC cm⁻². A SbO⁺ species adsorbed Pt electrode is obtained by introducing the fresh Sb solution continuously into the electrochemical cell. The irreversibly adsorbed SbO+ species begin to desorb when the potential is more positive than 0.50 V (vs Ag/AgCl). The reduction potential of irreversibly adsorbed SbO⁺ to metallic Sb atoms amounts to 0.11 V (vs Ag/AgCl). After the irreversibly adsorbed SbO+ species are reduced to metallic Sb, Sb atoms can be further deposited onto this Sb-modified Pt electrode in the way of UPD to increase the coverage of the metallic Sb monolayer. The UPD potential of antimony on the Sb-modified Pt electrode amounts to −0.07 V (vs Ag/AgCl). Finally, a Sb monolayer with the depositing charge 981 μC cm⁻² is obtained. Now the alternative deposition of Sb-Se compound by EC-ALE method is under study.