The effect of magnesium powder particle size on the combustion properties of Mg/PTFE fuel-rich propellant was studied. The thermal properties of Mg/PTFE were studied by using differential thermal analysis(DTA) and thermogravimetry(TG). The linear and molar burning rate were measured by high speed photography, and the flame temperature was surveyed by infrared radiation thermometers. The results show that reducing magnesium powder′s size had little weight on thermal analysis but steps up burning velocity even more than three times. The flame temperature of pyrotechnic fuel rich propellant heighten about 170 ℃ along with the diameter of magnesium powder decrease.