In this paper, a simple and effective pre-oxidation treatment method is proposed to strengthen reaction boned silicon carbide (RBSC). The effects of different temperature oxidation treatments from 800 ℃ to 1 300 ℃ on its microstructure and mechanical properties were investigated. Changes of residual flexural strength of materials with different sizes of pre-cracks before and after oxidation were also investigated. The results show that with the increment of the oxidation temperature, the strength and Weibull modulus of RBSC have a tend to first decrease, then increase, and then decrease again, mainly due to the different surface morphologies after oxidized at different temperatures. The flexural strength and Weibull modulus of RBSC increase significantly after pre-oxidized at 1 200 ℃ for 2 h, the strength increase by 19.9%, and the Weibull modulus increase from 7.3 to 11.8. However, both the incomplete oxidation at low temperature of 800 ℃ and the excessively strong oxidation reaction at high temperature of 1 300 ℃ lead to the decrease of flexural strength and Weibull modulus. Under the optimal pre-oxidation condition at 1 200 ℃ for 2 h, the residual flexural strength of RBSC specimen with indentation cracks (load of 20 N) increase from 201.1 MPa to 324.2 MPa after oxidation. The strengthening mechanism is that the SiO2 generated by high temperature oxidation eliminates the microcracks and defects of the material on the surface.