Unjust enrichment, which originated in Roman law, is one of the causes of legal obligations and forms a fundamental branch of civil law. In case that a person is enriched to the detriment of another person without juristic justification, there exists unjust enrichment with respect to the person so enriched. Legislation regarding unjust enrichment differs to a substantial extent from country to country. With expansion of international transactions in the meaning of civil law and/or business law, unjust enrichment under private international law grows in quantity and is becoming more and more complicated. Such unjust enrichment under private international law, which involves foreign element(s), reflects extension and development of civil law. Different rules regarding unjust enrichment adopted by different countries will result in conflict of laws. Therefore, it is of great importance to identify unjust enrichment and to determine the law to be applied thereto. This article tries to avoid the ordinary way of studying applicable laws solely on the basis of the theory of private international law. Instead, this article, based on an intensive study on such issues as the origin and development of the unjust enrichment system, its theoretical basis, formation and categories of unjust enrichment, points out the functions and value of unjust enrichment system. On the basis of the foregoing, this article, through comparative study on conflict of laws regarding unjust enrichment enacted by different countries, illustrates the significance and methods of identifying unjust enrichment concerning foreign element(s), establishes the reasonability of applying the lex fori to identification of unjust enrichment and discusses jurisdiction over unjust enrichment cases concerning foreign element(s). Referring to legislation practices, this article demonstrates several types in the principles of direct application, indirect application, flexible application of laws which apply to unjust enrichment, and proposes the legislative suggestions on the principles of application of unjust enrichment laws. Finally following the foregoing results of study, this article analyses the current situation of unjust enrichment in both substantive law and private international law and as a conclusion proposes legislative conception of structure of the unjust enrichment system in China.

不当得利源于罗马法的规定，为债的发生原因之一，是民法中的一项基本制 度,不当得利指无法律上原因，使他人受损而取得利益。对于不当得利制度，世 界各国民事立法规定存在很多差异，随着国际民商事交往的加强，国际私法上的 不当得利也日趋复杂和增多。国际私法上的不当得利含有涉外因素，是民法上不 当得利的延伸和发展，因各国法律规定的不同，在法律适用上会发生冲突。如何 对不当得利进行识别并准确地确定准据法，在不当得利法律适用中具有非常重要 的意义。本文试图摆脱片面依托国际私法理论探讨法律适用的研究套路，通过对 不当得利制度的产生发展、理论基础、构成要件、类型等基本理论问题的深入考 察研究，揭示不当得利制度的作用和价值。以此为铺垫，比较世界各国不当得利 制度的法律冲突及冲突原因和表现，论述了涉外不当得利识别的重要意义和识别 方法，阐述了法院地法作为不当得利制度识别的依据的合理性，论证了涉外不当 得利的管辖问题。参考各国立法例，论证了不当得利法律适用的直接法律适用原 则、间接法律适用原则、弹性法律适用原则中的几种具体类型，并提出了自己对 不当得利法律适用原则的立法建议。最后运用上述研究结论，分析了我国不当得 利在实体法上和国际私法上的现状，对我国不当得利制度的构造提出立法构想， 此亦为文章的结论。 关键词：不当得利 冲突 识别 管辖 法律适用