Consumer expertise is defined as the ability to successfully perform product-related tasks. The rapid development of the Internet era has made it more convenient for consumers to obtain expertise. Consumer expertise affects both their own purchase decision-making and the purchase behavior of others. Previous literature has studied consumer expertise from multiple aspects, but the research findings have not yet been systematically sorted and analyzed. For this reason, firstly, this paper clarifies the concept of consumer expertise, summarizes the sources of consumer expertise, and compares different research methods of consumer expertise. Secondly, it explores the psychological mechanism of consumer expertise from positive and negative perspectives, elucidates the effect of consumer expertise from the perspectives of self and others, and constructs a theoretical framework of consumer expertise. Finally, it identifies future research directions in four aspects of consumer expertise: conceptual categorization, the gap between subjective and objective expertise, the impact on oneself, and the influence on others. This paper could help firms understand the cognitive and behavioral differences between consumers with different levels of expertise and provide new insights for firms on market segmentation. In addition, it could help firms understand how consumers judge the expertise of other consumers, and improve their efficiency and effect of word-of-mouth marketing strategies.