Abstract :Sintering process has strong effect on the active surface area and catalytically active sites involved the catalyst. This process has two mechanisms depending on the thermal diffusion of the constituents of catalysts. These mechanisms are atomic migration model and crystallite migration model. Sintering is strongly temperature-dependent. However, there are different parameters affect in catalyst sintering such as time and type of atmosphere. Sintering process is the main factor in the catalyst deactivation. The deactivation of catalyst is the dramatic loss in the active surface area. Sintering process resulted in enhancement in the metal – support interaction yielding a side effect on the activity of catalyst. The scientists of catalysis have different works to reduce the negative effect of sintering process. These scientists showed various attempts to control in the dispersion and redispersion of active constituents of catalysts.