A controllable solid-state electrochemiluminescence (ECL) film based on efficient and stable quenching of ECL of ruthenium(II) tris-(bipyridine) (Ru(bpy)(3)(2+)) by oxidizing ferrocene (Fc) at the electrode is developed. The ECL intensity is correlated to the distance which is controlled by the conformation of the ferrocene-labeled DNA molecular beacon (Fc-MB) between the Fc and Ru(bpy)(3)(2+) immobilized on the electrode. The conformation adjustment is conducted via complementary DNA hybridizing with the bases in the loop of the Fc-MB and changing the temperature of the Fc-MB and the resultant double-stranded DNA (dsDNA). Those events all result in change of the ECL intensity. With such characteristics, the solid-state Ru(bpy)(3)(2+)-ECL film has the potential to be applied to reagentless DNA ECL biosensors and to calculate thermodynamic parameters of equilibrium constants of MB binding and the stem-loop formation.