In the system of SDS/n-C5H11OH/n-C7H16/H2O with the weight ratio of SDS/n-C5H11OH/H2O system at 5.0/47.5/47.5, the upper phase of the system was W/O microemulsion, and the lower phase was the bicontinuous microemulsion. When the n-heptane content was less than 1%, with the increase of the n-heptane content, the capacitance (C-o, Cod) in the upper phase (W/O) dropped, the capacitance (C-BI, C-BId) in the lower phase (BI) raised. At the same time, the W/O-BI interfacial potential (Delta E), capacitance (C-i), and charge-transfer current (i(ct)) decreased. After the n-heptane content reached 1%, with the increase of the n-heptane content, Delta E, C-i and i(ct) demonstrated no significant change.