In recent years, some cases involving legitimate defense disputes have sparked social discussion. This year's Spring Festival film "Article 20" once again brought the concept of "legitimate defense" to the spotlight in criminal law. In real life, each of us may face the threat of illegal infringement. How to respond correctly and how to protect oneself without infringing on the rights and interests of others are issues that everyone should consider and learn from. The social resonance triggered by the film "Article 20" comes from the practical issue it touches upon. It is centered around the legitimate defense system stipulated in Article 20 of China's Criminal Law, and through the real and touching story, ordinary people have a more intuitive and in-depth understanding of this legal provision. Article 20 of the Criminal Law of our country stipulates that legitimate defense and excessive defense are necessary. Its basic spirit is to provide timely self relief for those who have been wrongly infringed upon, as well as to provide guarantees for the immediate response of those who act bravely against illegal infringement, prevent them from being wrongly held criminally responsible, and send a clear signal to society to encourage those who act bravely. However, due to the particularity of legitimate defense, it is not easy to judge, define, and handle it in judicial practice. There have not been many cases recognized as legitimate defense over the years, which also indicates that the application of this important legal system is not ideal. It should be noted that since the formulation of China's Criminal Law in 1979, the recognition of legitimate defense has been quite strict. By the revision of the Criminal Law in 1997, legislative and judicial organs gradually realized that the recognition standards for legitimate defense should be appropriately relaxed to fully leverage the effectiveness of the legitimate defense system. However, in judicial practice, the recognition of legitimate defense is still relatively strict. Until recent years, starting from the Kunshan Anti Murder Case, there has been a gradual increase in cases of legitimate defense and an increase in social awareness. From a practical perspective, legitimate defense behavior is easily confused with physical altercation. In the absence of accurate judgment conditions, if one party dies or is seriously injured, the person who defends or acts bravely is easily convicted of the crime of injury. It can be said that the correct judgment of whether it is an intentional injury behavior or a legitimate defense behavior, and whether the perpetrator has the intention to fight or defend each other, are the key and difficult issues faced in the judiciary. Although the nature of legitimate defense and intentional injury is different, distinguishing them can be measured from the aspects of the purpose of the act, the target, and the result of the act. However, it is easy to know but difficult to act, and it is not easy to clarify the facts in litigation. The correct application of the legitimate defense system should not only avoid being too strict, but also ensure that it is not inappropriate. It should be noted that illegal infringement is sudden and urgent, the infringement behavior is difficult to control, and the consequences are unpredictable. Defenders or those who act bravely need to quickly and decisively take action to timely and effectively stop illegal infringement. Therefore, during this process, the actor does not have time to think repeatedly. If defenders or brave individuals are required to consider effectively stopping illegal behavior without causing unnecessary damage, it is not only unrealistic but also not in line with the public's simple cognition and values. On the contrary, it may make upright and brave people hesitate or even stand idly by. Therefore, in the process of making judgments afterwards, investigators from public security and judicial organs