Abstract: Stellite alloy deposition layer was prepared with micro-arc spark deposition technique on SCH13 steel. The microstructure, chemical compositions and phase structure of the deposition layers were examined by scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD),respectively. The formation and growth mechanism of a single pulse deposition spot were studied. The results showed that the single pulse deposition spot was in splash shape. A large number of the single pulse deposition spots were superimposed continuously and then a certain thickness deposition layers were formed. The deposition layer of SCH13 steel qrowed in a column crystal style,and the deposition layer had a good metallurgical combination with the SCH3 steels. The deposition layers were consisted of γ-Co solid solution and chromium carbides, and had a low dilution rate. The microstructure of the deposition layer was slightly coarser with the increasing of the processing voltage. The average hardness of the deposition layers increased significantly compared to that of the Stellite alloy electrode.