自20世纪50年代德国学者克鲁格使用“法律逻辑”这一术语以来，国外先后建立了以亚里士多德三段论逻辑理论等传统逻辑内容为基础的法律逻辑体系，和以一阶逻辑等现代逻辑内容为基础的法律逻辑体系。中国国内的研究情况也大抵如此。但是由于“形式逻辑只是研究形式，不管内容”，人们逐渐意识到法律逻辑研究应该以法律适用为出发点，即应强调法律实践中的内容认定与价值判断，并从法理学角度提出了“实质法律逻辑”的相关理论。但是，内容与价值似乎与逻辑并不相关，逻辑学家在研究法律逻辑的进程中处在了进退两难的局面。随后佩雷尔曼等提出了“法律逻辑是一种非形式逻辑”的观点，同时，法律实践中法律推理的可废止性表现出了司法实践中的法律推理很多时候是似真推理或者非单调推理，这就为非形式法律逻辑的研究提供了逻辑基础。法律逻辑中非形式逻辑的提出可谓为法律逻辑的研究开辟了一条新的道路，满足了法理学家与逻辑学家的共同愿望，并且有利于促进法律逻辑的研究沿着非形式逻辑的道路取得更多的理论成果。因此，非形式逻辑在法律逻辑中的重要地位日益凸显。本文通过法律逻辑的研究历程的分析，从法律逻辑的含义、研究对象入手，对法律逻辑中的法律推理与法律论证分别进行阐述，并以此为两个平台，试图探究法律逻辑中的非形式逻辑的重要作用，同时对其现有理论成果作一简单介绍。

Since the 1950s, German scholar Kruger use the term "legal logic" first, overseas has established the legal logic systems successfully, which is based on the traditional logic contents, such as the Aristotle syllogism logic theory and so on, and then take modern first-order logic contents as the foundation legal logic system. The research in China is probably the same. However, due to "formal logic studys on the form only, regardless of content", people are beginning to realize that the study of legal logic should be the starting point for the application of the law, that is, the content and value judgments in legal practice should be emphasized. And then, "the substance of legal logic" theory from the perspective of jurisprudence is made. However, the value and content do not seem relevant with logic. Logic scholars in the processes of legal logic are in a dilemma. Then, Perelman made a point of view that "legal logic is a informal logic". At the same time, it can be abolished in the legal practice，which show that legal reasoning of judicial practice is often a plausibility reasoning or a nonmonotonic reasoning. And it can be the logical foundation of the informal logic research. The study opens a new road for legal logic, which meets the common aspirations of legal scholars and logical scholars, and may help the study of legal logic along the path of informal logic of the theory to get more results. As a result, the status of the informal logic of legal logic will be important increasingly.This paper studies the process of legal logic analysis, and begins with the meaning of legal logic and the study start. At the same time, it elaborates legal reasoning and legal argumentation on the separate, and as a platform for the two, attempts to explore the importance of the informal logic in legal logic. And then, the existing theoretical results of informal logic in legal logic are made a brief introduction.