Standard thermodynamic functions (enthalpy, entropy, and Gibbs energy) and the heat capacity of the glass-forming AsxSe1−x system with their approximation to the low-temperature region are determined. The results were obtained using the combined technique, including dynamic calorimetry in the variant temperature-modulated differential scanning calorimetry and the unified model of the calorimetric and volumetric properties of glass and melt. The thermodynamic functions for unstudied AsxSe1−x glasses with intermediate composition were predicted on the basis of the parametric similarity of properties determined by the model. The temperature dependences of the density and the coefficient of thermal expansion are determined. Using the method of quantum chemistry, the geometry of As2Se3 glass net was found and its Raman scattering spectrum was calculated. The thermodynamic functions of the AsxSe1−x glass-forming system, which is the basis for the formation of novel promising glasses with functional additives, are necessary to determine the conditions for their synthesis based on the method of minimizing the Gibbs energy.