Abstract: Gaseous phase products and thermodynamic parameters of various charcoal/KNO<SUB<3</SUB< compositions are calculated using the least free-energy principle. From the point of view of reaction kinetics theory, simulation results are analyzed and ratios of compositions optimized. Taking ratio of gas products, force of the powder and temperature of explosion as target functions, low corrosion and environmental-friendly sulfur-free black powders were designed and their thermodynamic properties improved. The physical, chemical and output properties of the optimized compositions compared with normal black powder. Results show that the sulfur-free black powder is more sensitive to flame, and insensitive to impact and electrostatics. The output power is also considerably higher than the normal composition.