lang=EN-US>The diagenesis, reservoir space and controlling factors of Mesozoic clastic reservoirs in Zhuanghai area have been researched in this paper through core observation, thin section determination, scanning electron microscope and X-diffraction analysis.The results show that, the clastic reservoirs experienced strong compaction, cementation and metasomatism as well as polyphase dissolution and crack formation.The diagenetic processes can be divided into four stages including early diagenesis B, middle diagenesis A1 and A2 and middle diagenesis B.There exist two chief types of reservoir space: the one is fractures including structural fractures, compaction fractures and cleavage cracks,the other is secondary pores including feldspar dissolution pores and carbonate cement pores which are related to atmospheric water dissolution and organic acid dissolution during the course of organic matter evolution in Shahejie Formation and Dongying Formation.The Mesozoic clastic reservoirs in Zhuanghai area are lang=EN-US>chiefly affected by sedimentation, diagenesis and tectonism.