The justifiable defense is the law entrusts with a citizen's important right, is encourages and safeguards the citizen to make struggle's important means with the illegal criminal acts, regarding the safeguard country, the public interest and citizen's legitimate rights and interests, the deterrent criminal offender, stops and the prevention of crime, has the positive significance and the function. The new criminal law even more specific stipulation justifiable defense's protection object was “the country”, “the public interest” is exempt from the criminal the unlawful attack. Transferred the general citizens to make struggle's enthusiasm and the self-conscious justifiable defense with the illegal criminal acts is the law entrusts with us each citizen's right, was also in the citizen morality and justice duty. The correct implementation justifiable defense is not only advantageous in stops with the prevention unlawful attack, defends the legitimate rights and interests, moreover is advantageous in brings honor to the healthy tendency, promotes the socialist ideological and ethical progress. key word: Justifiable defense. Defense system. Infinite defense. Fights mutually. Body carrying weapon for criminal. Instigation. Defends has worked as