Under the impact of the financial tsunami, global economy was weaken, lots of luxury brands¡¦ profits decreased, but trendy brands rise at that time. There are many kinds of trendy brands appear in Taiwan since 2008, and become famous between young people immediately. Trendy brands emphasize with uniqueness¡Bself-expression, not only become the fashion tendency, they also play an important role in teenagers¡¦ sub culture. As trendy brands get popular, some companies want to attract more young people by cooperating with trendy brands. Crossover with trendy brands is the main topic for companies. There is a lack of research about trendy or crossover so far, so this study is based on co-branding theory, analysis the change of consumers¡¦ evaluations about Positive brand emotions, negative brand emotions, involvement, and brand identity after company crossovers with different kinds of trendy brand. Then the study adds fitness between company and trendy brand and self-construal types of consumer as mediators, trying to comprehend the influence. This study finds consumers¡¦ evaluations about positive brand emotions and negative brand emotions will be better if company crossover with trendy brand founded by famous people. But consumers¡¦ evaluations about brand identity will be better if company crossover with both trendy brand founded by famous people and ordinary people. However, fitness between company and trendy brand and consumer¡¦s self-construal types don¡¦t change evaluations after crossover.