The application of the hydrostatic pressure modifies the height of the barrier, the effective masses and the thicknesses of the Multi-Quantum Wells (MQWs) constituting. We apply a hydrostatic pressure on a perfect GaAs/GaAlAs MQWs; this pressure modifies the structure of the electronic band, which leads to modification of the energies of the electrons states. So in order to show the effect of the external pressure on the proposed structure, we studied the variation of the electronic transmission as a function of the energy of the incoming electronic wave, for different applied pressure values. The electronic states are moving towards low energies when we increase the hydrostatic pressure. Besides, the application of hydrostatic pressure on MQW structure with defect layer, shows the important sensitivity of the induced electrons defect states on the intensity of the applied pressure.