A method for studying the effect of some organic compounds, that are neither soluble in water nor to be made into soluble salts in water on DNA has been investigated by a series of experiments. The solubility experiments have shown that dimethyl sulphoxide(DMSO) and its aqueous solutions are excellent solvents for the hydrophobic multicycles compounds with nitrogen atoms. The data of UV(298 K), CD(298 K), ~(31)P-NMR(323 K) spectra and molar enthalpy changes (298 K) for the effect of DMSO on DNA have not shown any effect of DMSO on DNA when the pH of solution is equal 7.0 and its concentration is less than 0.15 mol·L~(-1). The results of UV (298 K), CD(298 K) spectra and molar enthalpy changes (298 K) for the effect of eight multicycles compounds with nitrogen atoms on DNA in aqeous solution of DMSO have indicated that two of them have strong intercalation binding to DNA. Both the mechanism of interaction between the above compounds and DNA and the relationship between the behavior of intercalation binding of the compounds with same multicycles structures to DNA and their microstructures have been discussed.