Abstract: This paper analyses the cause of low-porosity, low-permeability of sandstone from both sides of miscrocosmis angle and the evolution of diagenesis. And synthetically concluded that compaction not only get the container rock's physical property worse, but also apt to get less maturity sandstone densify. With enlargement of the buried depth, diagenesis of sandstone will be continue at the circumstance that no hydrocarbon compound accumalated. At the same time, when the top and bottom of sandstone within the mudstone is located the output from which compacted fluid enter into sandstone, the sandstone easy to be densified.