In this article we report the results of photoluminescence studies on In0.25Ga0.75 As-GaAs straiaed quantum wells grown by molecular beam epitaxy under pressure at 77 K. The applied hydrostatic pressure ranges from 0 to 50 kbar. The pressure coefficients of T valley of (InGa)As-GaAs strained quantum wells are presented. We have observed the crossover between the energy level in the well and X valley in the barrier GaAs. With the analysis of its behavior under pressure, the ratio of conduction band offset to valence band offset in In0.25 Ga0.75 As-GaAs heterojunction is determined as Qc =△Ec:△Ev = 0.68:0.32. The theoretical studies on (InGa) AsGaAs strained quantum wells under normal pressure fit the experimental results very well. Some discussions about (AlGa)As-GaAs quantum wells are also included in this paper.