Abstract: The adsorption isotherms of c'yanine dyes Ⅱ and Ⅲ (1-methyl-1'-(γ-sulfopropyl)-2,2'-cyanine Ⅱ and its 6'-methyl analog Ⅲ) on AgBr suspensions in several solvents were obtained at 25℃ by centrifugation method. Corresponding absorption (reflection) spectra of these dyes in solutions and in adsorbed states over a wide concentration range were recorded. The solvent effect on dye adsorption and on the aggregation states of dye molecules were discussed. The very small heat effect in dye adsorption was measured at 25±0.01℃ with the Versatile Precision Semiconductor Calori-metric System developed in this lab using a specially designed calorime-tric unit. The precision environmental temperature control to 25±0.0001℃ is implemented by a microcomputer system. The isosteric molar heat of adsorption of dye Ⅱ in DMF-Water (1:1) to AgBr was obtained at 25℃ to be (3.18 ±0.09) kJ/mol (θ=0.87). Also calorimetric measurements were made for adsorption of dye Ⅱ in DMFto AgBr over a wide concentration range, and the isotherm expressed in terms of enthalpy per m² AgBr surface was drawn with the shape essentially in parallel with that obtained from the phase separation method. This result shows that the precision calorimetry can be used for the study of dye adsorption process.