In recent years, new oil reservoirs have been discovered gradually in yan8 subsection of Yanan Formation in Linzhen area, Ordos basin. It is important to understand the reservoir characteristics of yan8 subsection for further explo-ration and exploitation. On the basis of drill-core samples observation and study on rock thin section, the reservoir charac-teristics and Porosity evolution of Yan8 subsection of Yanan formation were analyzed. The results showed that:The sand body in the northeast side of the study area is rather thick, which is high-quality reservoir in the study area. The maturity of composition is on low side and structural maturity is middling;The main type of pore is residual intergranular porosi-ty,dissolved pores between grains and dissolved pores in grains;The author holds that the diagenesis is in the A substage of late diagenesis period;Original porosity of reservior is 33.6%in the stage of sedimentation, and the lithogenesis of compaction, cementation and dissolution are main factors affecting reservoir properties in this area;The compaction and carbonate-cementation destroy the primary-texture of pore intensively, which contribute 16.7%and 10.7%to the loss of original pores, respectively. The dissolution plays an important role in improving the properties by producing secondary porosity and has increased the 6.8%secondary pores.%近年来林镇地区延安组延8油层组中不断发现新油气。利用岩心观察、薄片鉴定等分析手段，对储层特征及成岩作用进行研究，定量分析成岩过程中储层孔隙演化特征。结果表明：研究区东北部一带砂体连续，厚度普遍在14 m以上，为该区优势储集体；储层砂岩矿物成熟度较低，结构成熟度中等，沉积时环境相对稳定；孔隙类型以溶蚀孔为主，残余粒间孔次之；该储层目前达晚成岩阶段A期。储层原始孔隙度为33.6%，其演化过程主要受压实作用、胶结作用和溶蚀作用控制，压实及胶结作用导致原始孔隙度丧失16.7%与10.7%，后期溶蚀作用形成6.8%次生孔隙，有效地提升了延8油层组储层的孔隙度。
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