A novel photoelectrochemical strategy for the sensitive determination of p-nitrophenol (PNP) was developed using a glassy carbon electrode (GCE) modified with CdSe quantum dots (QDs) and DNA composite film (CdSe-DNA/GCE). Various surface analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), were employed to characterize the synthesized CdSe QDs and CdSe-DNA modified electrode. The interfacial behaviors of the modified electrodes were analyzed by electrochemical impedance spectroscopy (EIS), and the interaction between PNP and DNA was studied by UV-visible spectrometry. Due to the PNP-DNA interaction, CdSe-DNA/GCE exhibited a sensitive photocurrent response toward PNP under visible-light irradiation. The influencing factors, such as the concentration of DNA used for fabricating CdSe-DNA/GCE and the bias potential applied in the photoelectrochemical measurement, were investigated. Under the optimized conditions, the photocurrent on CdSe-DNA/GCE was linearly increased with the PNP concentration from 0.7 to 50 μmol L(-1), with a detection limit (3 S/N) of 0.27 μmol L(-1). The proposed photoelectrochemical strategy was successfully applied to monitoring the degradation of PNP.