Nowadays，with the rapid development of power grid，the critical clearing time（CCT）is required to be shorter and shorter，while the breaker failure is exerting more and more influence on system stability.Based on a description of the main factors of the fault clearing time，including the protection releasing time，the inherent breaker opening time，the arc extinction time and current element returning time，the distribution and maximum of each component are analyzed，and the setting and logic optimization of both breaker failure prevention and dead-zone prevention are proposed.The proposed optimization strategy is now applied in China Southern Power Grid.