The dissolution behaviors of nitrogen, carbon and cyanide in binaries, ternaries and high order slag systems in the CaO–MgO–Al₂O₃–SiO₂, CaO–B₂O₃ and Na₂O–B₂O₃ systems are thermodynamically modeled in the present study using the hybrid model which is an integration of the capacity model and the modified quasichemical model. In combination with previous FACT thermodynamic oxide database, the present model can well reproduce the dissolution behaviors of nitrogen, carbon and cyanide both in the basic slag and acidic slag regions simultaneously using surprisingly small number of model parameters. In particular, the solubility minima of carbon and nitrogen in molten slags are also well explained by the model.