SiC-mullite brick is widely used in the upper and lower transitional zones of cement rotary kilns, due to excellent thermal shock resistance, and abrasion resistance. The investigation of different bauxites was made on the performance and micro-structure of SiC-mullite brick, especially thermal shock resistance. In two batches of bricks (G1 and G2), and two grades of bauxites (L1 and L2), samples’ physical and chemical properties were tested, and microstructure and phase composition were studied by SEM and XRD. The results show that raw material L2, containing large numbers of micro-pores smaller than 4 μm, has well developed mullite phase. While using L2 as aggregates and fines, SiC-mullite brick G2 has excellent thermal shock resistance. Therefore, for manufacture of SiC-mullite brick, not only chemical composition, bulk density and open porosity of bauxite are important, but also its microstructure has to be considered, such as phase composition, crystal size and pore size distribution.