Abstract: Electric-spark deposition (ESD) process was developed since the beginning of this century. Because the discharge time is short and the bonding strength of deposition layer is strong,the ESD process is widely used for materials life extension and surface modification. In this paper,an automatic electric spark deposition system,a high-speed camera and metallurgical analysis technique were used to analyze the process of electric-spark depositing YG6 on Cr12MoV mold steel. The effect of electrode pressure on the deposition surface roughness and deposition rate was analyzed. The optimal electrode pressure parameter (1.6 N) was obtained after a large number of experiments. In the deposition process with 1.6 N electrode pressure,spark discharge occurred mainly with subsidiary short circuit discharge, and the deposition efficiency was high with low surface roughness.