Abstract: The pore evolution and storage capacity of oil and gas reservoirs are controlled by various types of diagenetic fluids, which are the key factor for reservoir development. However, the conventional petrographic methods are challenging to identify the types of multiphase diagenetic fluids and their influence on pore transformation in the diagenetic process. The Ordovician diagenetic fluids in Gucheng area are determined by integrating petrographic and geochemical methods, so as to further clarify the control effect of various types of diagenetic fluids on reservoir development. The results show that, there are 10 phases of diagenetic fluids with various types in the process of carbonate reservoir development in the study area, including quasi-contemporaneous atmospheric freshwater, quasi-contemporaneous medium salinity evaporated seawater, shallow buried medium salinity sealed seawater, medium-deep buried organic acid water, medium-deep buried formation brine, phase Ⅰ hydrothermal fluid related to albitization, phase Ⅱ deep brine fluid related to hydrothermal recrystallization, phase Ⅲ magnesium poor hydrothermal fluid related to exogenous fluid, phase Ⅳ silicon rich fluid related to siliceous development, and phase Ⅴ calcium rich fluid related to the late calcite filling. By analyzing the influence of diagenetic fluids in each phase on reservoir development, it is concluded that the quasi-contemporaneous atmospheric freshwater and phase Ⅲ magnesium poor hydrothermal fluid played a constructive role in the development of high-quality reservoirs; The phase Ⅳ silicon rich fluid related to siliceous development had dual reconstruction on reservoir development; The local high-quality reservoirs can be formed by hydrothermal corrosion.