无效合同制度是法律对合同自愿原则的必要干预,通过对合同的否定性评价来引导当事人的缔约行为,其制度价值在于维护社会公共利益。无效合同是指欠缺合同生效要件、不受法律保护的合同。本文从无效合同的概念和特征着手,详细阐述了无效合同的情形,最后指出无效合同的法律后果。 Invalid contract system is the necessary intervention of the law on the principle of voluntary contract, and through the negative evaluation of the contract to guide the party's contractual behavior, the value of the system lies in safeguarding the social public interest. Invalid contract is the lack of contract entry into force elements, not the legal protection of the contract. This article starts from the concept and characteristic of invalid contract, elaborates the situation of invalid contract, and finally points out the legal consequences of invalid contract.