The electronic structures and intersubband absorption coefficients of Ge0.3Si0.7/Si/Ge0.3Si0.7 quantum wells with barrier-δ-doping grown on Ge0.3Si0.7(001) substrates are consistently calculated in the envelopefunction approach. The dependences of the absorptivities on the well widths, δ-doping position and δ-doping concentration are discussed . At last, the frequency shift caused by the depolarization effects of highly dense two-dimensional electrons are studied.