【摘要】 基于合同的相对性原理 ,合同之债主要是一种对内效力 ,即对合同当事人的效力。但是法律为防止因债务人财产的不当减少而给债权人的债权带来损害 ,允许债权人对债务人和第三人的行为行使法律所规定的权利。这些权利的行使 ,实际上涉及到第三人并对第三人产生法律的拘束力。而且由于合同变更与合同转让 ,给第三人的权利义务也产生了重大影响。因此 ,对不同情况下第三人法律地位的确认 ,能更好地保护合同当事人以及第三人的合法权益更多还原

【Abstract】 Based on the relativity of contract , the obligation of contract mainly has internal effect on the concerned parties. In order to prevent the damages to the claimer caused by the indecent increase in the obligor’s property, the law allows the claimer to have the rights based on the obligor and the third person’s deeds. In essence, those rights involve the third person and can bring about legal restrictions on him. Meanwhile the change and transfer of the contract will also have big effect on the third person’s right and obligation.As a result, the definition of the third person’s position in different cases can help the protection of the rights and interests of the concerned parties and the third person.更多还原