Abstract: The mixed potential as a function of time was measured during the electroless copper plating on ceramic and copper substrates, and the induction process was determined successfully. The effects of the chelating agents, additives and pH value on the mixed potential－time curves were investigated. The results indicate that the mixed potential－time curves shift in negative direction and the induction time becomes longer with increasing concentration of the chelating agents or the additives in the solution. And higher pH values in the solution can shorten the induction time and make the potential－time curves more negative. The activation process can affect the induction time, higher activation temperature decreases the induction time greatly and increases the plating rate at the same time. It needs much longer induction time for plating copper on fresh-copper-activated copper substrate than that on the Pd-activated copper substrate. On the basis of these results, we furthermore explained the reason why non-noble-metal activation process is inferior to noble-metal activation process in electroless copper plaing.