Intense room-temperature midinfrared luminescent emission has been observed in PbTe/CdTe quantum wells. A theoretical model is developed to study the spontaneous emission and optical gain of the new hetero-structure. In the model the discrete energy level is calculated based on the k·p envelope function method and finite-confinement-potential approximation. Strain effects and anisotropic band structure characteristics of PbTe are taken into account. The dependences of spontaneous emission spectra on intraband relaxation and carrier density are investigated. It is shown that the calculation results are in agreement with the experimental data of photoluminescence. For PbTe/CdTe quantum wells (QWs) with well width of 20 nm, two emission peaks are dominant in the spontaneous emission spectra, which blueshift with carrier density increasing while intraband relaxation is considered in calculation. The shift of ground state emission is from 372 meV to 397 meV and that of the first excited state emission is 15 meV, as the carrier density increases from 2×1017 cm-3 to 2.8×1018 cm-3. The shifts of transition energies are attributed to carrier-carrier and carrier-phonon scattering mechanisms. As compared to the PbTe bulk material, the PbTe/CdTe QWs have higher and broader optical gain, which make them a promising material for mid-infrared laser operating in continuous-wave mode at room temperature.