This paper study the delay of destructive breakdown and its mechanism on SiO2 films by TCE treatment. The result show that the breakdown current capacity increase with increasing the TCE flow-rate, treatment time and temperature, and reducing the oxygen partial pressure. However, excessive quantity of the TCE flow-rate and prolonging of treatment time make the breakdown characteristics degradation begin to appear. The results also indicate, the increment of breakdown current capacity is associate with the increment of density of electron trap in SiO2 films. In this paper, we propose a breakdown model of "low barrier point-electrical field enhanced" which involve three processes of mutual reinforcement, and consider for the first time the effect of H2O in TCE oxidation on the breakdown characteristics. The restrained function of electron trap on electrical field enhanced in low barrier point is quoted, and analyze the mechanism for delay of destructive breakdown in TCE oxides.