Based on 15 key cores and several hundreds of reservoir analysis data，the fan delta sand bodies of Shahejie Formation in Zhanhua Sag, Jiyang Depression, Bohai Bay Basin, are consisted of feldspathic sandstone，which mainly experienced compaction，cementation，dissolution and replacement during the burial diagenetic evolution，and now the diagenetic evolution came to the middle diagenetic stage at current burial depth of 1800~4000m. The dissolution of feldspar played a significant role in improving reservoir quality during the burial diagenetic evolution. The intergranular pores and intragranular pores，caused by the feldspar dissolution in the depth of 2800~3300m，are constructive for the reservoir properties in increasing the porosity and permeability (the porosity may be up to 30% and the permeability up to 1000×10-3μm2). Obviously，to find the depth where the dissolutions and the secondary pores developed is favorable for predicting good quality reservoir.