The simultaneous occurrence of H₂S and CO₂ exists during many processes, and they react with each other to form COS and H₂O. Here, we develop a novel non-fitting functional representation regarding the chemical equilibrium constant subject to the reaction of H₂S and CO₂. It depends only on standard experimental data for the concerned five molecular constants of CO₂ and COS and six molecular constants for H₂S and H₂O, and possesses the advantages of direct algebraic operation and convenient application, whereas the conventional empirical correlations involve multiple adjustable coefficients for fitting experimental data. The average absolute deviations between three experimental data sets of the equilibrium constants and the theoretical values predicted with the developed functional representation are 4.33 %, 5.73 %, and 5.93 %, respectively, while the corresponding deviations of three same experimental measurements from the theoretically calculated results with the previous empirical correlation provided in the well-known Aspen databank are 19.1 %, 73.6 %, and 10.0 %, respectively. Through a comparison of the theoretically predicted results of the equilibrium constants with the experimental data, we find that the presently proposed prediction formulation based on considering the structural characteristics of molecules is reliable, while the corresponding empirical correlation given in the well-known Aspen databank is not applicable. This study provides a novel approach to predict the chemical reaction characteristics involving highly toxic sulfur-containing compounds.