Cyclic voltammetry and chronopotentiometry were used to investigate the electrochemical behavior of Tm3+ ion in the 0.01 mol dm(-3) Tm(NO3)(3)/0.1 mol dm(-3) LiClO4/DMSO system on a Pt electrode. The experimental results indicated that the reduction of Tin 31 ion was irreversible. Some electrochemical parameters were measured. The cyclic potential deposition technique was used to prepare Tm-Co alloy films. In a nonaqueous system, we first reported the preparation of rare earths and their alloy films by cyclic electrodeposition. The surfaces of Tm-Co alloy films observed by scanning electron microscopy (SEM) were uniform, adhesive, compact and showed a metallic luster. Tm-Co alloy film was amorphous as proven by the X-ray diffraction (XRD).