Abstract: A new iterative method is proposed for the calculation of equilibrium compositions of gases, at high temperatures. In this method, the iterative processes for temperature and for composition are all performed in one step. Thus, for a given initial state of the gas mixture and known quantity of beat addition, the equilibrium composition and temperature can be calculated in one series of iteration, instead of several as in the older methods. The saving on the laborious calculation will be especially evident when the composition is more complex. The method can be applied to both non-flow equilibrium states and isentropic flow processes with chemical equilibrium existing at any instant.