he study of diagenetic characteristic about reservoir rocks is one of the core issue to the reservoir research, and it is essentially prior to reservoir evaluation and prediction. In this paper, various diagenesises occurred . in Xujiahe sandstone are analysed by slices samples which are systematically and carefully observed. The genesis and its effect on the pore developing are discussed in the diagenesis stages later, based on which the diagenesis phases of sandstone in Xujiahe Formation are classified in the study area, and its diagenetic succession is then established. The result indicates that: intense compaction, pressure solution and early cementation of calcite are the key to significant loss the primary pores in Xujiahe sandstone. And, underground acid fluids lost their active s-pace, which makes dissolution immature and reservoir particularly tight. According to the classification discipline of elastics diagenesis phase, the sandstone of Xujiahe Formation experienced sorts of diagenesis, where its intensity is significant and is now in late substage-B diagenesis phase.%通过对川东北地区须家河组砂岩薄片样品的系统鉴定和研究,详细分析了它们所经历的各种成岩作用,探讨了这些成岩变化的发生机理及其对储层孔隙的影响程度,划分了研究区须家河组砂岩的成岩阶段,并建立了其成岩演化序列.研究结果表明:强烈的压实、压溶作用和早期方解石胶结作用是造成本区须家河组砂岩原生孔隙大量消失的关键因素,同时使地下酸性流体失去活动空间,导致溶蚀作用不发育,储层异常致密；根据碎屑岩成岩阶段划分规范,须家河组砂岩经历了多种成岩变化,成岩作用强度大,目前已处于晚成岩B亚期.
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