Abstract：Western natural law is the foundation of western legal theory.It originated in ancient Greek city-states period.After the Stoics development it formed a complete system，and then through the further development with ancient Rome jurists such as Cicero ，it had a huge influence on Roman law.After entering the middle ages Aquinas elaborated it as the divine nature of law.Until modern times by Grotius，Hobbes and other classical natural jurists‘ reinterpretion ，it had a lot of new contents.
　　Key words：analysis；western natural；law thoughts
　　Firstly，the ancient natural law thoughts
　　The idea of natural law originated from the ancient Greek city-states and it came from the ancient Greek’s understanding of nature.They believed that nature is sacred，and there is a chain in the nature that human can not see.The chain specifies the natural order and the action of everything in the world .That we can’t see what is known as the natural order of the chain should be the supreme principle of human behavior.Human must abide by piety without breakthrough.It is the foundation of the law and justice.For the definition of natural law thoughts，the wise school contributed a lot.The school of sophists made a detail analysis of ‘nature’ and they explained the environment and social life of human beings with natural things or natural laws.From the perspective of nature and physiology，this paper expounds the idea that everyone is equal.It is believed that there is no difference on people who are all skull toes.In real life，the difference on people is completely caused by the system and it is the result of man-made laws.Human beings should act in accordance with nature，not in accordance with artificial laws，and human beings should act in accordance with higher natural laws.
　　Secondly，theocracy natural law thoughts
　　Theocratic natural law thoughts flourished in Europe in the middle ages，among which the most important representative was Thomas Aquinas，who put forward the theological theory of natural law.After combining augustine’s theological legal thoughts with Aristotle’s naturalistic natural law thoughts，Aquinas believed that natural law is the law that rational people get higher than positive law through their understanding and comprehension of god’s eternal law，which is the bridge between positive law and god’s eternal law.Aquinas further explained that eternal law is the reason of god，it is the supreme law governing all things in the universe.The law of nature is a rational person’s understanding of the eternal law of god，So the actual law enacted by the state organs must be subordinated to the natural law，and finally to the eternal law of god. 　　Thirdly，the classical natural law thought
　　The classical natural jurists no longer take divinity as the basis of natural law，but they hold that natural law is a legal principle applicable to the state of nature and it can be derived from human reason .And these legal principles are higher than actual law in efficiency.The classical natural jurists，though slightly are different in their ideas of natural law，are consistent in their general views.They believed that natural law is connected with the state of nature and social contract，and it is the common law in the state of nature before the formation of human society.The core of these principles，which are in line with the fundamental interests of human beings，is human freedom and equality.Moreover，in the application of natural law，the classical natural jurists demanded that any positive law that does not conform to the natural law should be abolished and reformed ruthlessly.According to the classical natural jurists，the natural law constructed by human reason has its self-evident，consistent and necessarily essential properties，which even god cannot change.It is the foundation of positive law and it is the standard to measure the good and evil of all behaviors.
　　Fourthly，conclusion
　　This paper starts from the source of the natural law thoughts，and runs through the whole history，make a simple analysis of its characteristics and content in each historical period.In order to clarify the boundary and scope of the concept of natural law，the author believes that the idea of natural law ，with its innate advantages，will continue to play an important role in the future development of jurisprudence.
　　作者簡介
　　邢光太（1990—），男，汉，山东省聊城市人，研究生在读，青岛大学，研究方向：中国法制史。