It is demonstrated that the Paleogene reservoir came through compaction, cementation and other diagenesis by the analysis of lab data.The mechanical compaction was main one, not the compaction-dissolution. The cementaion involved quartz growth, carbonate and clay mineral formation.The carbonate cements formed in two fifferent phases,the clay calcite was developed in the early phase on the shallow strata, but the crystal calcite on the middle-deep strata.The dissolution of calcite and feldspar was obvious.The pore evolution went through primary to secondary pores.The pore size was affected by the dissolution of calcite and feldspar,as well as cementation of carbonate.The early cementation of calcite was favorable for the late the development of secondary pores.There was a different depth of secondary pore development in different regions in Jiyang sag.From the west to the east in Jiyang sag, the depth of secondary pore growth was increased,that was 1500-2400m in western Huimin depression, 1650-2450m in middle Dongying depression,then 2200-2700m in Chezhen depression and 2300-3500m in Zhanhua depression ,the characteristics of secondary pore distribution was influnced by the migration of sedimentation center.