In order to clarify the diagenetic types of shale and their effects on shale reservoir development，the shale of Upper Es4 to Lower Es3 Members in Dongying Sag is taken as the research object. The diagenetic type was studied through core and thin section observation，SEM，EDS，XRD，and elemental analysis. The diagenetic stages were divided in combination with analyses on vitrinite reflectance，rock pyrolysis and I/S mixed-layer ratio. Meanwhile，the diagenetic evolution characteristics were also determined and the effects of diagenesis on the spatial development of reservoirs were clarified.The results show that the diagenesis types of the shale of Upper Es4 to Lower Es3 Members in Dongying Sag include formation of pyrite，dolomitization，compaction，cementation，dissolution，recrystallization，clay mineral transformation and rupturing，etc. The diagenetic evolution had been in the middle diagenetic stage A. The formation of pyrite，dolomitization，recrystallization，clay mineral transformation are beneficial to the formation of intercrystalline pores，dissolution is favorable for the formation of grain inner pores，and rupturing can form fractures.