Cooperation and alliance between brands has become an innovative and efficient marketing strategy. By cooperating with brands in other industries, enterprises can not only expand their own market areas, but also use the brand influence of partners to quickly attract the attention of consumers and enhance brand awareness and reputation. However, in the process of co-branding, many companies ignore the role of explanation strategy. At the same time, there are few researches on brand product fit and corporate explanation strategy at present, and there is no conclusion on the research path. The purpose of this study is to explore the influence path. Based on conceptual combination theory and symbolic interaction theory, this paper explores the influence mechanism of product fit and firm interpretation strategy on consumer brand co-evaluation. Design co-branding scenarios for different product categories (coffee, body wash and cocktails) through three sets of experimental designs. Data were collected through questionnaires, and 615 valid questionnaires were collected. SPSS27.0 was used to analyze the data to test the different responses of consumers to brand co-evaluation in the match between different product fit and enterprise explanation strategy. This paper confirms the interaction between product fit and firm explanation strategy on consumer brand co-evaluation. Among them, when the brand alignment is high, compared with the property mapping interpretation strategy, the relationship link interpretation strategy can make consumers have a higher evaluation of the brand alignment. Compared with the relationship link interpretation strategy, the property mapping interpretation strategy can make consumers have a higher evaluation of the brand association when the product fit is low. It also verifies the mediating role of information processing fluency and the moderating role of consumer involvement. The research shows that when enterprises adopt the brand cross-border joint strategy, they should choose the appropriate propaganda and explanation strategy according to the product fit degree with the cooperative brand. And simplify the way of product presentation, promote the fluency of consumers' information processing, and should also adopt different publicity strategies according to different levels of consumers involved.

Co-branding, Interpretation Strategy, Information Processing Fluency, Consumer Involvement, Consumer Evaluations