E-commerce have adopted a series of preventive measures to control in the United States, the European Union, Japan and other developed countries, and our country is in the early stages of online shopping development. Therefore, to promote the healthy development of e-commerce and maintain the stability of the economy and society, it is particularly important to study online shopping fraud, which has a strong practical significance. The in-depth study based on a large number of domestic and foreign literature, the study found that has been widely studied by many domestic and foreign scholars have this problem, this problem has aroused the attention of experts and scholars at home and abroad, but most of them are based on personal information security, online recom·mendation and other issues, the research methods are more focus on data analysis and evidence theory etc. Firstly, using the framework of law case base, and calculates the similarity of the case with the nearest neighbor method, which relates to the determination of the weight, the design method of the analytic hierarchy process and make some adjustments, and then identified as fraud in online shopping provided strong basis.