In recent years, the fashion industry has set off a trend of co-branding, and co-branding has become a unique marketing strategy for major brands to obtain benefits. However, there are potential risks when brands are selecting joint partners. The literature in this paper addresses both the positive effects of co-branding and how it is viewed from a business and customer perspective related to customer loyalty. Besides, previous researches on how to correctly select joint partners have not been explored in the collected literature. Therefore, the purpose of this study is to provide a deeper understanding of the strategy of choosing partners for brands from a negative aspect under the current trend of brand cooperation，and to propose relevant implications through case analysis. The research method used in this paper is qualitative research by conducting case studies and four focus groups. The findings indicate that communication and connection are the basis for two brands to having success. Furthermore, the enterprise needs to evaluate and estimate the capabilities of the partners by analyzing the external environment and opportunities. Besides, with the help of co-brand partners, brands can make up for their shortcomings and work together to achieve the expected goal.