Abstract: VASP code was used to study the ideal tensile process of oxygen doped SiC in this paper. The effects of the oxygen interstitial and substitution models on the mechanical property of SiC were studied. The results show that a brittle deformation occurs in the tensile process of oxygen doped SiC after the peak of stressstrain curve, indicating the change of mechanical property of oxygen doped SiC. The tensile strength and Young’s modulus of SiC with different oxygen doped models were calculated. The results show that compared with the bulk SiC, both the tensile strength and the Young’s modulus of oxygen doped SiC are reduced in some extend.