Abstract: The effect of the kind and content of silica fume, the contents of magnesia fine and sodium tripolyphosphate (STP), and particle size distribution coefficient (Andreasen coefficient) on the theological property of bauxite-based Al₂O₃-MgO castable were researched with a new developed castable rheometer. The results show that under vibration conditions, the castable has characteristics of the Bingham model, with shear-thinning and thixotropic property. The type of silica fume has some effect on the rheology of the castable. The content of silica fume in the range of 3% to 5% has significant effect on the theology of the castable; with the increase of silica fume's addition, the rheology of the castable gets better. At the particle size of magnesia fine in this experiment, the content of magnesia fine in the range of 4% to 12% has little effect on the rheology of the castable. The addition of STP in the range of 0.13% to 0.19% has obvious effect on the rheology of the castable. With the increase of STP's addition, the rheology of the castable get better, but the effect gets worse at the addition of 0.19%. The best addition of STP is 0.15% to 0.17%. With the increase of particle size distribution coefficient in the range of 0.23 to 0.31, the water demand for the same flow value is decreased, and the rheology get better too, but no more effect when higher than 0.29. There is good relevance between the rheology and flow ability. The better the rheology, the better the flow ability is.