Abstract: The reservoir quality is strongly influenced by the depositional facies and diagenesis of the Chang 2 sandstones of braided river facies in Qinghuabian oil field．It is suggested that the depositional facies controls reservoir quality by the grain size and clay minerals content of the sandstones，as a result，the reservoir quality of the main sandbodies within the braided rivers is better than both sides sandbodies of the braided river，while the reservoir quality of the depositions between braided rivers is the worst．It is also indicated that diagenesis is another key factor modifying reservoir properties，and the mechanical compaction is the main factor which caused the loss of primary porosity for the sandstones，carbonate cements，secondary enlargement of quartz are the main cementation that reduced the reservoir quality of the sandstones，while the reservoir quality for the braided river sandstones was improved by dissolution．So the braided river sandstone reservoir will be the dominant aims of exploration in this area for the future.

Key words: Qinghuabian oilfield, reservoir quality, diagenesis, depositional facies