Abstract: In order to study the effect of ambient atmosphere on the coal ash slagging on the surface of corundum liner, the slag samples from the high-temperature slagging experiments were analysed by Scanning Electron Microscopy(SEM), Energy Dispersive Spectrometer (EDS) and X-ray diffraction(XRD), and the slagging samples' properties of morphology and the sintering characteristics between ash compositions and corundum under different atmospheres were studied. The results show that under oxidative atmosphere, the basic substance can promote the cohesive action between coal ash and corundum refractory liner, especially the aluminum rich corundum refractory liner, in which the nucleating and crystaling reactions occur. Under reducing atmosphere, Fe³+ is transformed into Fe²+ in the ash to form eutecticum compounds with low melting temperature, which will increase the bonding degree between molten ash slag and corundom refractory liner, and the segregation and slagging-resistant effect of Fe, Cr, Ti is weakened