The heat capacities C_p and excess heat capaciries C_pE of four binary systems cyclohexanone-benzene, cyclohexanone-toluene, cyclohexanone-elhylbenzene, cyclohexanone-isopropylbenzene are measured at 298.15K and under latm by the Calvet microcalorimeter. The error of mole fraction is ±0.0002, of C_p±0.0085, of C_pE±0.055, and of temperature ±0.01K. The C_pE values of the four systems are always positive for whole ranges of mole fractions. The excess heat capacities decrease with the increase of number of carbon atoms of aromatic hydrocarbon. The experimental results are at variance with the Prigogine-Flory corresponding state theory. The effect of changes of solution orientational order on C_pE is also investigated. The intermolecular orientational order entropy parameter θ2S12 is introduced to the Flory model. The Flory model including θ2S12is improved for the estimation of C_pE values.