The idea of the principle of proportionality can be traced back to the British Magna Carta, and people should not be severely punished for minor crimes. /kloc-in the 9th century, the concept of the principle of proportionality first appeared in German police law, and then the principle of proportionality developed greatly in theory and practice. Otto Meyer, a German administrative law scholar, argued in the German Administrative Law published by 1895 that "police power should not violate the principle of proportionality". In the third edition of the same book, 1923 holds that "going beyond the principle of necessity is illegal abuse of power". At the beginning of the 20th century, Fleiner, another German administrative law scholar, described the limits of police's exercise of power with the famous saying "Don't shoot birds with cannons" in his book "German Administrative Law System". It is argued that the conceptual result of action is the legal embodiment of the principle of proportionality. The Prussian Police Administrative Law (193 1) stipulates that police punishment must be necessary to be legal. At the same time, article 14 of the law defines necessity as: "In order to maintain public safety or order, or to effectively defend against the danger of endangering public safety or order, the police organ may choose one of them, but the police organ shall try its best to choose the method that causes the least damage to the parties concerned and the general public." This legislative model has been widely adopted by German states. [1] In judicial practice, the then High Administrative Court took whether the measures taken by the police exceeded the necessary limit to achieve the goal as one of the contents of the review. With the development of democracy and legal system, the principle of proportionality later surpassed the field of police law and was given constitutional status by the German federal court, but its core content is still that administrative costs should maintain a reasonable proportional relationship with administrative effects. The principle of proportionality requires that the administrative activities of administrative subjects should pay attention to reasonable proportion and coordination within the statutory scope.