— The effects of fuel injection angles on the average diameter of fuel propulsive droplets sizing and efficient mass fraction in combustion chamber of a ramjet are numerically investigated in the present paper. We named the mass of fuel vapor inside the flammability limit as the efficient mass fraction. In order to investigate the effects of fuel injection angle on the mean diameter of fuel propulsive droplets sizing, there are conducted two sets of calculation. The fuel injection angle of part I is varied as 30°, 45°, and 60° in flow direction, also the fuel injection angle of part II is counter-flow and varied as 0°, 30°, 45° and 60° to examine its effects on the fuel droplets and fuel/air mixing phenomena, as well as we have increased the fuel injection velocity from 40 to 45, 50 and 55m/s respectively and we have inspected the needed data again. To fulfill the calculation we used a modified version of KIVA-3V.