Mullite-cordierite sagger is particularly important for the preparation of high-performance lithium battery cathode materials. In this paper, mullite (1.18~0.6 mm) and cordierite (2~1 mm) were used as aggregates, and mullite (0.074 mm), calcined alumina (0.044 mm), Foshan yellow mud (0.044 mm) and coal gangue (0.044 mm) were used as matrix. Mullite-cordierite sagger for lithium battery cathode material LiNixCoyMnzO2 (LNCM) was prepared by sintering at 1 380 ℃ for 3 h. The corrosion behavior of cathode material on sagger during sintering process was investigated by burying corrosion method. The results show that the mechanical properties and thermal shock resistance of sagger sintered at 1 380 ℃ for 3 h are good. The flexural strength at room temperature is 10.02 MPa, and the residual strength retention rate is 51.52%~53.26% after three thermal shock cycles. The corrosion resistance of mullite-cordierite sagger can be effectively improved by appropriately increasing the content of coarse particles (1.18~0.6 mm) of mullite. After 25 times of erosion, the maximum reaction layer thickness on sagger surface is 447 μm, and the minimum reaction layer thickness is 211 μm.