Chemical equilibrium compositions, total temperature and total pressure of HF chemical laser combustor for NF₃-D₂-He reaction system were calculated by combining minimum Gibbs' free energy method and mass flux conservation principle. Mole flux of F atom as a new parameter that can be used to express yield of F atom was presented. The effect of changing fuels' mass flow rates on combustor's characteristics was analyzed with emphasis. When the compositions proportion in combustor was maintained constant, increasing of mass flow rate of F atom and total pressure of combustor was in proportion to the increasing of total mass flow rate. Changing of total pressure had no obvious impact on adiabatic flame temperature, degree of F₂ dissociation, and mole fraction of F atom. The changing of mass flow rates of NF₃ or D₂ was able to adjust the oxidizer excess factor. In comparison with changing mass flow rate of D₂, changing mass flow rate of NF₃ could acquire much higher mole fraction and mole flux of F atom, much smaller fluctuating amplitude of combustor's total pressure. Increasing mass flow rate of He decreased adiabatic flame temperature and mole fraction of F atom observably. Whereas degree of F₂ dissociation and mole flux of F atom maintained a high level still when primary diluent ratio was less than 15.