In this article we investigated the effect of different redox probes (Ru(NH3)(6)(3+), Fe(CN)(6)(3-/4-), methylene blue(MB)) on electrochemical identification of DNA single nucleotide polymorphisms (SNPs) by chronocoulometry (CC), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Thiol-modified probe DNA (p-DNA) and mercaptohexanol (MCH) were co-assembled on Au surface to form p-DNA/MCH mixed self-assembled monolayers (SAMs). The surface coverage of p-DNA (Gamma(p-DNA)) on Au was adjusted by changing the concentration ratio of p-DNA and MCH (Cp-DNA/C-MCH = 1: 100 or 1: 1) for mixed assembly. The p-DNA/MCH SAMs on Au were hybridized with complementary DNA (c-DNA) or mutant DNA (m-DNA) in solution, and the SNPs sites of mutant DNA were located at up, middle and down positions of hybridized DNA duplex. Experimental results showed that DNA SNPs could be identified using Fe(CN)(6)(3-/4-) or MB as the probes but using Ru(NH3)(6)(3+). Furthermore, the identification effect of DNA SNPs was closely related to Gamma(p-DNA). DNA SNPs could be identified more easily by Fe(CN)(6)(3-/4-) at lower Gamma(p)-DNA and by MB at higher Gamma(p-DNA). However, the SNPs positions (up, middle or down) could not be identified obviously using Ru(NH3)(6)(3+), Fe(CN)(6)(3-/4-) or MB. (c) 2018 The Electrochemical Society.