Abstract: Single walled carbon nanotubes (SWCNT) modified glassy carbon electrode (SWCNT/GCE) was fabricated. The electrochemical behavior of nitrophenols isomers at SWCNT/GCE was investigated by Cyclic Voltammetry (CV). Two pairs of quasi-reversible redox peaks for m-nitrophenol (m-NP) and p-nitrophenol (p-NP) were observed. The potential difference of the oxidation peaks for nitrophenols isomers was 0.19 V, indicating that the simultaneous determination of m-NP and p-NP at this SWCNT/GCE was feasible. The effect factors of the electrochemical response of nitrophenols isomers were optimized by linear sweep voltammetry (LSV). Under the optimum conditions, two linear calibration plots of the peak current and their concentration for m-NP and p-NP were obtained in the range of 2.7×10-6～1.0×10-4mol/L and 2.0×10-6～1.0×10-4mol/L, respectively. Their oxidation peaks current increased direct proportionally with the scanning speed, which suggested that the electrochemical oxidation of nitrophenols isomers was adsorption -controlled process. Based on Nicholson method, the rate constant of electrode reaction could be estimated, concurrently, and the substitution constant (ρ) of Hammett reaction was calculated by using Hammett equation.