Because of the degradation of side linings and cathode blocks, some aluminum reduction cells (300 kA prebaked anode type) were shut down for relining in Yichuan aluminum smelter plant. Combining with actual observations, the samples of side linings and cathode blocks were analyzed from different locations of the cells, and the reasons for degradation of the Si3N4-SiC side linings and cathode blocks were investigated. Also, the factors influencing degradation of cathode blocks and side linings were summarized as superheat temperature, anode effect coefficient, space from anode side to the sidewall and current density. Some suggestions are offered to solve these problems for the large scale prebaked anode reduction cells in China.