Diagenesis is defined as the process involving physical and chemical changes in sediment after deposition that converts it to consolidated rock. Carbonate rocks are mainly composed of carbonate minerals only and have a polygenic origin, and thus are different considerably from clastic and pyroclastic rocks. Quantitative and qualitative changes of grains (mineral composition and chemistry) and pores (petrop-hysical properties such as porosity and permeability) in carbonate rocks during each stage of dagenesis (compaction, fracturing, solution, cementation and transformation) were discussed in detail. The conclusion is that diagenetic changes in carbonate rocks is chiefly controlled by the chemistry of fluids (pH, Eh and ions) in pores rather than the physical factors such as overburden pressure, geothermal temperature and geologic time.