The prepared LC\-4 billet with SLMA technology and LC\-9 billet with liqudius-quenching were used to investigate microstructure evolution of Al-Zn-Mg alloy in semi-solid state during hot working. The law of microstructure evolution for the two kinds of alloy in semi-solid state during hot working was quite different because the SLMA technology was fully different from liqudius quenching. Grain size of LC\-4 grew up due to coalescence while the microstructure of LC\-9 didn’ t show any evident change. Microstructural component after and before hot working semi-solid state was analyzed by SEM and energy spectrum analysis. The results showed that the grain boundary was composed of eutectic area, area rich in Cu with low melting point and impurity area. Moreover, the liquid film of reheating microstructure for LC 9 alloy was thicker than for LC 4 alloy, and the composition of the workpiece in different part in semi-solid state after hot working is basically even, which has verified the lamellar flow model for the billet in semi-solid state during hot working.