Red beds are widely distributed sediments on Earth with specific environmental significance. It is generally believed that hematite cement formed under water oxidation conditions is the main color-producing mineral. At present, the research on red-bed coloring minerals mostly remains at the level of mineral identification, lacking in-depth study on their microscopic occurrence states and genetic mechanisms. Taking the continental red beds of the Lower Cretaceous Zhidan Group in the Ordos Basin as an example, this paper adopts multi-scale characterization techniques of core, thin section, cathodoluminescence, and argon ion polished scanning electron microscopy to reveal the microscopic occurrence of nano-scale colorant-hematite cement in red bed sandstone for the first time, and re-explore its genetic mechanism on this basis. The study found that the colorant of red bed sandstone, hematite cement, is mainly needle-like or sheet-like, with two microscopic occurrence states: one is encapsulated and developed around the edges of clean sandstone particles, with individual mineral particles ranging in length from 500-1000nm and width below 50nm; The other type of filling development occurs in the cleavage fractures of clay minerals and mica particles, often arranged in a directional manner along the cleavage. Due to the spatial constraints of the cleavage fractures, individual mineral particles are smaller, with lengths generally less than 500 nm and widths below 30 nm. The occurrence and occurrence state of hematite in red bed sandstone indicate that it was formed by the early dehydration of limonite, followed by the development of two phases of calcite cementation. Therefore, hematite cementation should mainly occur during the sedimentation and shallow burial periods, rather than during the uplift period after sedimentation. The formation process of hematite cement in sandstone indicates an environment characterized by high atmospheric water oxygen content under a dry inland sedimentary background, which is also a glacial state during the geological history. This suggests that the red sandstone of the Lower Cretaceous Zhidan Group in the Ordos Basin also has important implications for studying the global glacial state during this period.