Qianmiqiao Oil Field consists of Ordovician carbonate buried-hill reservoirs that lie under Beidagang Belt in Huanghua Depression. The buried hill experienced a complex uplifted and buried history due to multiple faulting and/or folding deformations during Mesozoic to Cenozoic eras so that the reservoirs,in which different kind of anisotropy pore spaces formed by fracturing, karstification and cementation, was in control of late hydrocarbon migration and emplacement. By analysis of diagenesis process of carbonate reservoirs,it is suggested that effective pore spaces in the buried hill are fractures that formed by deformation and meteoric karstification during Mesozoic intensive deformation stage and then complicated by selective solution and cementation during Tertiary buried stage, which strongly reshaped reservoir textures and dismembered seepage flow units so as to cause disconnected spaces for fluid flow. Fracture-pore system and hydrocarbon-supplying “windows” may co-affect the hydrocarbon migration and accumulation net, and further predominate distribution of hydrocarbon in the buried hill reservoirs. It is proposed that Qianmiqiao Field is of the fractured reservoirs controlled by carbonate diagenesis but not of block reservoirs controlled by connective karst pores.