Abstract: In recent years, much attention has been paid to slurry dimethyl ether synthesis technology due to its advantages in heat transfer, isothermal condition and efficient energy utility. However, the catalyst stability is a bottle-neck to restrict the commercial application. This paper studied the structure and physicochemical properties of Si-Al based catalyst prepared by the complete liquid-phase method. The catalysts were characterized by XRD, TEM, XPS and XRF technics, and then contrasted with traditional hybrid catalyst. The results indicated that there were different reason in their deactivation. Hybird catalyst deactivation was caused by Cu sintering, gathering and specific surface area decreasing. For Si-Al based slurry catalyst, the Cu loss during the reaction was an important reason leading to deactivation.