A simple experimental method of light emitting diode (LED) injection efficiency (IE) determination was suggested. IE and internal quantum efficiency (IQE) calculation is an actual and difficult problem in LED science. In this paper IE and IQE of blue LEDs were determined separately. The method is based on electroluminescence data fitting by themodified rate equationmodel. Efficiency droop caused by Auger recombination and poor injection were taken into account. Only one reasonable assumption was accepted during the calculations: IE tends to 1 at low current densities.