In the actual industrial production process, it is usually appropriate to reduce the cooling rate and control the residual stress. In this study, the Time-Temperature-Property curve of Al-Mg-Si alloy sheets was measured by interruption quenching and subsequent artificial aging method. The microstructure evolution of Al-Mg-Si alloy was carefully characterized using optical microscopy (OM) and transmission electron microscopy (TEM). It was found that the nose temperature of the TTP curve drawn by experiment was ~360°C, closing to the nose temperature of ~365°C obtained from the simulated TTT curves. The number of equilibrium phase rapidly increased with the increasing of holding time, while no obvious equilibrium phase formation at the low temperature region and high temperature region. The critical cooling rate is 14.3°C/s, the determination of the critical cooling rate has important reference value for the control of alloy sheet during quenching process in the actual industrial production. The quenching sensitive region of the Al-Mg-Si alloy sheet is between 290°C and 440°C.