Being different from diagenesis of argillutite that is mainly secular compaction, the diagenesis of carbonate rock is mainly cementation and metasomatism so that carbonate rock almost lose all of primary pores and depositional water in it. The carbonate rock is in the perfectly enclosed environment of compacting fluid with deep burial. Besides of small-scaled pressure solution that is formed by deep burial and geothermal rise, other styles of diagenesis are faint. After organic matter enter the depth of hydrocarbon generation threshold, low abundance of organic matter may generate an amount of hydrocarbon but carbonate rock may not cast off such same great deal of compaction water as the argillutite. Due to neither carrier of hydrocarbon migration nor dynamics of abnormal pressure with fracture-generating condition, hydrocarbon compounds are difficult to come out from its parent rock in largescale. Hydrocarbon compounds may be dispersed in disconnected intercrystalline pores and form crystal-wrapped organic matter combined with minerals and inclusion enclave organic matter, which results in hydrocarbon percentage of carbonate rock commonly higher than that of argillutite.