In order to investigate the fatigue fracture resistance of Si₃N₄ bonded SiC refractory ceramic under the oxidation conditions at high temperature, the relationship between the strength and the size and the strength and the density of the micro-cracks were simulated by the effective field-subdomain model and the thermal-damage breaking model.The results show that the feasible scope of the size between (0 mm, 0.5 mm] and the density of the micro-cracks between (0 m^-2,10⁴ m^-2] can keep the fatigue fracture resistance of these materials under the oxidation conditions at high temperature.The application is good to extend the service life of materials and ensure the safety and stability of equipment operation.