In this paper, the effects of temperature and NaF on the properties, crystal structure, and morphology of corundum-mullite materials prepared from fly ash and bauxite were studied in detail by XRD and SEM. The results indicate that the relatively low sintering temperature of 1200℃ can be obtained by adding 2% NaF, which helps effectively to promote sintering during the solid reaction, and that the obtained materials have excellent properties: bulk density 3.08 g/cm3, flexural strength 62.11 MPa, and the content ratio of mullite/corundum 2∶1. WhenNaF content rises to 4%, mullite assumes the long columnar form in network structure, with the single crystal aspect ratio ranging from 6 to 10; nevertheless, the lower mullite content in this sample results in relatively low mechanical strength. When NaF content rises to 8%, mullite phase disappears, and the main phase of the material is corundum, with the appearance of a large amount of albite, which mostly develops into crossed corn-like crystal clusters under the SEM.