A conductivity equation based on the dual-disk microelectrode was derived. This electrode was used for in situ measurement of the conductivity of polyaniline. Some factors such as electrochemical potential, solution pH, scan rate and over-oxidation, which influence the conductivity of polyaniline, were conveniently controlled by this electrode. Experimental results proved that this electrode is very useful for measuring the relative conductivity in situ and studying the conducting mechanism of conductive polymers.