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The excess heat capacity at glass transition temperature in two types of glass-forming systems of [xNaNO3\cdot(1-x)KNO3]60[Ca(NO3)2]40 (0 \leq x \leq 1) and Ca(NO3)2\cdotyH2O (4 \leq y \leq 13) is studied. In the former system, with the replacement of K+ cation with Na+ cation, the excess heat capacity is almost invariable around 65.1 J\cdotmol-1\cdotK-1, while the excess increases by 38.9 J\cdotmol-1\cdotK-1 with the increasing per molar H2O content in latter system. A quantitative description of the excess heat capacity is built up with the consideration of atomic and molecular translational motion in the glass-forming systems. This finding might offer further understanding to the glass transition.