Double electrostatic films are formed in deoxyribo nu cleic acid(DNA) molecule. The dyestuff are adsorbed and the adsorption spectrum changes. In this report,the microsurface adsorption-spectral correction techniq ue is applied to investigation of the interaction of DNA with night blue(NB) at pH 3.63 and pH 7.07. The results show that the adsorption of NB on DNA obeys the Langmuir monolayer adsorption.