It is an effective strengthened technique to introduce a coating containing compressive stress on the surface of ceramic. In this work, the mixed slurry of alumina and quartz powder was coated on the pre-sintered alumina body, then the mullite-alumina coating with lower thermal expansion coefficient was synthesized in-situ after pressureless co-sintering. The pre-stressed strengthening of alumina was achieved by the residual compressive stress formed in the coating during the cooling process. The results indicate that, with the increase of the doping content of quartz in the coating, the flexural strength of pre-stressed alumina increases firstly and then decreases. The flexural strength of specimen realizes the highest value when the doping mass fraction of quartz is 15%, and the interface between the coating and the substrate bonds tightly. Under this condition, the flexural strength of the pre-stressed alumina ceramic is (549.44±27.2) MPa, which is 37.19% higher than that of the common alumina. When the doping mass fraction of quartz is higher than 15%, the flexural strength decreases due to the shrinkage stress mismatch in the sintering process. The effect of prestress enhancement weakens gradually with the increase of temperature. As the testing temperature reaches and exceeds 1000 ℃, pre-stressed alumina and common alumina possess approximately equal flexural strength. Pre-stressed alumina also exhibits better thermal shock resistance and damage tolerance due to the compressive stress formed in the coating