Abstract: Based on the analysis of thin sections, cathode luminescence, electron probe, laser carbon, oxygen isotopes and inclusion thermometry, three periods including five cement types were observed in the dolomite reservoir of the 4th member of the Leikoupo Formation in Longmen Mountain front. Distribution characteristics and development degree indicated a reduction of the influencing process on pore cements. Phase 1 cement is dolomite. Its deposition is the main stage that leads to the porosity decline of the blue green algae agglutinate dolomite. However, after the cementation, the residual porosity has some supporting protection, and a large number of early pores are preserved. Phase 2 cement is the vadose silt that causes reservoir inhomogeneity of the blue green algae agglutinate dolomite. Phase 3 cement is the ferric calcite. These late diagenetic products generally filled in the pores of micritic-silty dolomite to further reduce the reservoir porosity, but this cement was inhibited by the organic acid. Therefore primary pores are well preserved in the long reburial stage.