To understand the initial oxidation of the stretched perfected 3C-SiC nanowire, the stable atomic configurations of an O atom adsorption on the 3C-SiC ((1) over bar2 (1) over bar) surface were investigated by first-principle calculation. The results show that the stress-free 3C-SiC ((1) over bar2 (1) over bar) has 1 x 2 periodicity due to the surface reconstruction. The strongest O atom adsorption happens at B2-3 site in the stretched 3C-SiC ((1) over bar2 (1) over bar) with the adsorption energy around -5.6 eV, consistent with the results of the stress-free 3C-SiC ((1) over bar2 (1) over bar). This is because that the relative position between the O atom and the oxidized Si atoms does not change with the stretching. The adsorption energies of the O atoms at T-1, T-5, T-6 and B-6 sites on the surface of the stretched 3C-SiC ((1) over bar2 (1) over bar) increase, resulting from the decreased stability of the topmost oxidized Si atoms and the outstretched distance between two Si atoms. Therefore, though 3C-SiC nanowires are used as reinforcements under tensile strain in practical applications, the stretched perfected nanowires aren't easilier oxidized than the stress-free ones with retaining their toughening effect.