In this work, a series of modified electrodes were constructed and studied by means of electrochemical impedance spectroscopy, including ssDNA/MWCNTs/GCE (E1), dsDNA/MWCNTs/GCE (E2), TSPP/ssDNA/MWCNTs/GCE (E3) and TSPP/dsDNA/MWCNTs/GCE (E4), for the detection of DNA sequences specific to HER2 gene—a tumor marker related to several kinds of common cancers. Here, ERBB2 is linked to cancer.