We report the phototransmission measurement of strained‐layer InxGa1−xAs/GaAs single quantum well structures at room temperature. The spectra obtained show distinct features of excitons in the single quantum wells. Fitting of the phototransmission spectrum indicates that the excitonic transition energy modulation is the main mechanism. The phototransmission can be used as a supplement to photoreflectance due to its sensitivity and convenience.