Diagenesis and its corresponding cements are extensively developed in the Upper Carboniferous phylloid algal reef, Houchang Town, Ziyun County. These cements are prominent and representative in Houchang Town. A study of crystal shape, fabric and cathodoluminescence images of cements as well as the contacts between cements can help determine paragenetic sequences, recognize diagenetic environments, and understand the porosity evolution in the phylloid algal reef limestones. Only limestone that has a great deal of secondary porosity generated during the catagenesis stage could become oil and gas reservoirs in the Nanpanjiang Basin.