A novel method for DNA detection was developed based on the excellent fluorescence properties of cationic conjugated polymer ( CCP)and the target DNA enrichment,separation function of nanoparticles. First,the quencher-labeled DNA capture probes were modified on the surface of Au nanoparticles,and complementary DNA strands were captured. Second,S1 nuclease was added,and the capture probes that had not captured the complementary DNA were removed from the nanoparticles.Finally,the complementary double-stranded DNA was cut by Dnase I,the quenchers were dissociated from nanoparticle and the fluorescence of CCP was quenched by means of combination of quenchers and CCP.The results showed that this method is specific.In the range of 5. 0 -40 nmol/L,the concentration of target DNA was proportional to the fluorescence quenching and the detection limit was 3.7 nmol/L(S/N = 3).