Abstract: This is an article in the field of ceramics and composites. Rheology and microstructure properties of iron-doped tailings 3D printing cementitious materials were studied in this paper. The results show that the particle size of tailings is small and can be used as aggregates for 3D printing materials. In the 3D printing process, it can smoothly pass through the pipeline for conveying the cementitious material. As the content of iron tailings continues to increase, the shear viscosity of 3D printing cementitious materials shows a trend that first decreases and then stabilizes in the region. However, the changing law of shear stress shows an increasing trend as the interval between layers increases. The compressive strength and flexural strength of 3D printing cementitious materials both show a decreasing trend. When the interval between layers is in between 20～30 min, the compressive strength and flexural strength decrease more slowly. As the interval between layers continues to increase, the interlayer bonding strength of 3D printing cementitious materials shows a decreasing trend. The 3D printing cementitious material with 30% iron tailings content is hydrated for 90 days after XRD diffraction test. The main material components of the cementitious material are quartz, ettringite, calcite, albite, perovskite, Ca₂SiO₄ and seven substances such as calcium silicate hydrate.