In this paper, DNA/carboxyl MWCNTs was immobilized on a glassy carbon electrode (GCE) to develop an electrochemical sensor for simultaneous determination of liquiritigenin (LG) and liquiritin (LQ). The adsorptive voltammetric behaviors of LG and LQ at DNA/carboxyl MWCNTs composite film modified GCE were investigated by differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The calibration curves for LG and LQ were obtained in the ranges of 0.08-1.60 mu M and 5.0-100.0 mu M with the detection limits of 0.02 and 0.8 mu M (S/N = 3), respectively. The method was applied successfully for the detection of LG and LQ in human blood serum with satisfactory recoveries. It provides a new tool for the research of the pharmacological mechanism of LG and LQ in vivo. (C) 2019 The Electrochemical Society.