The influence of steady LED irradiation on the photocurrent spectra of the strained layer multiple quantum wells In0.15Ga0.85 As (8nm)-GaAs (15nm) with 15 periods have been studied from 10 K to 300 K. The photocurrent peaks corresponding to various transitions decrease in different ways with the increase of LED irradiation intensity. By this means, the transitions from confined subband to continuum can be identified easily, and the conduction- and valence-band edge discontinuity has been determined directly from the experimental energy values of various transitions. Consequently, the band offset of heavyhole valence band is obtained as Qv = 0.38±0.01.