The method is based on the enhancement effect of the resonance light-scattering (RLS) of pararosaniline by DNA. In the pH rang of 0.5-1.5, the enhanced intensity of pararosaniline RLS at 355 nm is proportional to the concentration of DNA in the rang of 0.20-15 micrograms.mL-1. The detection limit is 36 ng.mL-1. This method is simple, rapid and has been applied satisfactorily to the determination of DNA in mixed samples.