In big data era,data has become a key element in social production and economic development,and there is enormous potential value in personal information in improving government decision-making,enterprise's precision marketing,innovation of social management and so on. Globally,the legislation of personal information protection law represented by the European Union has become the mainstream practice in the international community. As for the definition of personal information,the international community has basically formed an approach based on identifiability. But the dynamicity and contextual nature of the definition of personal information not only leads to the difficulty of judicial application,but also makes the enterprise not be able to deal with the problem of anonymization appropriately. In order to make up for the inherent defects of personal information definition,it is necessary to take full advantage of foreign legislation,strengthen the top-down design of personal information rights and construct a prior consent,risk evaluation and case-based mechanism,which constitute the proper meaning of promoting the rationality of civil code and personal information protection law in the future.