The petrologic characteristics，diagenesis and major controlling factors of reservoir quality of the Liushagang formation in Huachang-Bailian area, Fushan depression, Beibuwan basin are analyzed by means of physical properties analysis, casting thin-section, X-ray diffraction and SEM. This study shows that the reservoir of Liushagang formation, characterized by litharenite and lithic sandstone, is low porous and permeable with dissolved intergranular and intragranular pore as the main pore type and then the residual primary pore. The reservoir in research area is mainly affected by combined factors of depositional environment and diagenesis, whose original porosity is medium and strongly reformed by later diagenesis. Currently, the Liushagang reservoir is at late diagenetic phase A.The main diagenesis types in Liushagang reservoir are compaction, secondary enlargement of quartz and cementation of authigenic clay mineral, etc. It is the compaction that reduces the primary pore space in Liushagang reservoirs, while dissolution generated secondary porosity that improves reservoir quality. By comprehensive analysis of the structure, deposition, diagenesis, the result shows that the favorable reservoir in the Fushan depression is mainly distributed in the relatively higher parts of braided delta front sandbodies.