A fluorescent method based on copper/silver nanoclusters for the detection of Cu2+ was established by designing DNA sequences with G rich bases and investigating the fluorescence enhancement effect of G base pairs on DNA-Cu/AgNCs.It was found that the fluorescence intensity of the prepared DNA-Cu/AgNCs was significantly enhanced by the G5 sequence at the 5′ end of the C rich sequence template.Meanwhile,the fluorescence of DNA-Cu/AgNCs was quenched by Hg2+ and Cu2+.NaBH4 could be used to mask Hg2+ in order to achieve a selective detection of Cu2+.The linear range of this method for Cu2+ was from 0.01 μmol/L to 5.0 μmol/L,and the detection limit was 5.0 nmol/L.The method is simple,rapid,highly selective and low cost,and is able to apply in detection for real samples.