Abstract: The natural fractures generated by geological movement can form the lattice structure pattern in the sedimentary rocks. Crystal growth of carbonate mineral in these pre-existing fractures result in the calcite sealing in the limestone. In this study, mineralogical composition was analyzed and the concerns include hard minerals and water sensitive minerals. Water saturation can affect the minerals content and lead to water sensitive damage. Uniaxial compression experiment was carried out on the cylinder-shaped samples of the Carboniferous limestone containing calcite veins. Complete stress-strain relationship of the compression experiment combined with CT scanning results reflect two aspects for the role of calcite vein in the mechanical behavior of limestone under compression conditions. One aspect is the structural effect played by the interface between calcite vein and host rock, and another aspect is the joining of the thick calcite vein together with the host rock to resist compression. Significant brittleness of the limestone containing thin calcite veins is illuminated through the experimental results. More plasticity and lower strength are shown with thickness increase of the calcite vein in the limestone.