Dolomitization is one of typical diagenesis in carbonate rocks, the Middle-Lower Ordovician shallow marine carbonate rocks of Yingshan Formation in Tahe area is important oil- gas bearing reservoirs and pervasively dolomitized. Focused on the special dolomitization confied by stylolites in the limestone of Yingshan Formation, this paper attempts to reveal the diagenetic conditions and dolomitization processes of this type of dolomites. Based on detailed petrological studies, cathodoluminescence, 86Sr/87 Sr ratio,δ13C-δ18O isotope and oxygen thermometer of dolomites and matrix limestone are analyzed, and these geochemical results indicate that dolomites confined by stylolites in limestone of Yingshan Formation occurred in shallow burial diagenetic environment which was relatively reductive, and the remnant sea water in micro-pores supplied the fluids for dolomitization, and Mg2+ released by high-Ma calcite stabilization during burial diagenesis probably supplied Mg2+ for dolomitization. However, relatively limited diagenetic fluids and Mg2+ supply in the relative closed diagenetic conditions limited the scale of dolomitization and the development of dolomite. Analysis of poroperm of dolomitic limestone and pure limestone show that the contribution of dolomitization on absolute poroperm is relatively limited. However, some oil filling in dolomitization parts in limestone probably indicate that this kind of dolomitization can afford potential conduits for small scale oil-gas migration and deep hydrothermal fluids flow.