A microelectrode ͑ME͒ has been developed to replace rotating disk electrode ͑RDE͒ for in situ monitoring of additives in copper plating baths by cyclic voltammetric stripping ͑CVS͒. Details on the relationship between the dimension of ME and the rotation speed of RDE producing same mass transfer rate were described. The results in theory showed that the stationary ME can reach a very high mass-transfer coefficient which is comparable to that at RDE with high rotation rate. Comparison of CVS studies between ME and RDE showed that a good agreement was obtained in analyzing additives in a copper plating bath, containing chloride ions, polyethylene glycol, 3-mercapto-1-propanesulfonate, and Janus Green B or some combination of them. The similar tendencies of curves for different additive packages indicated that effects of additives on copper electrodeposition are the same at both electrodes. Furthermore, results of sample analysis also showed positive evaluation to ME. It was proved that ME might be a substitute for RDE which monitors additive concentrations in copper and other metal plating baths.