To ascertain the reservoir characteristics and the physical properties controlling factors ofDongying Formation is the premise of the efficient development in L oilfield in Bohai Bay. Based on core observation, combined with thin section observation, scanning electron microscope, cathodeluminescence and physical property analysis, this paper studied and analyzed the reservoir characteristics, diagenesis and pore evolution under the guidance of reservoir geology theories. The result shows that the sandstone of Dongying Formation in L oilfield has the characteristics of lowmineral maturity and textural maturity. The main diageneses are compaction, cementation, metasomasis and dissolution. The diagenesis roughly experienced early diagenetic A and B stage and late diagenetic A stage, and now it is in the late diagenetic B stage. The diagenesis has great effects on controlling the physical properties in the study area. During the pore evolution, the compaction and the cementation are destructive, while the dissolution is constructive.