In the present work,single-walled carbon nanotube (SWNT) is firstly used to establish a laser-induced fluorescence (LIF) based DNA biosensor in order to discriminate different single base mismatch locations on a certain oligonucleotide.Since the dye-labeled single strand DNA (ssDNA) can helically wrap to the sidewall of SWNT due to then-stacking interaction,the fluorophore is efficiently quenched by SWNT.