We obtained the high mobility of μ2K=1.78×106 cm2/V·s in Si-doped GaAs/AlGaAs two-dimensional electron gas (2DEG) structures . After the sample was illuminated by a light-emitting diode in magnetic fields up to 6 T at T=2K, we did observe the persistent photoconductivity effect and th e electron density increased obviously. The electronic properties of 2DEG have b een studied by Quantum-Hall-effect and Shubnikov-de Haas (SdH) oscillation measu rements. We found that the electron concentrations of two subbands increase simu ltaneity with the increasing total electron concentration, and the electron mobi lity also increases obviously after being illuminated. At the same time, we also found that the electronic quantum lifetime becomes shorter, and a theoretical e xplunation is given through the widths of integral quantum Hall plateaus.